Law is a set of rules decided by a particular place or authority meant for the purpose of keeping the peace and security of society.

Courts or police may enforce this system of rules and punish people who break the laws, such as by paying a fine, or other penalty including jail. In ancient societies, laws were written by leaders, to set out rules on how people can live, work and do business with each other. But many times in history when laws have been on a false basis to benefit few at the expense of society, they have resulted in conflict. To prevent this, in most countries today, laws are written and voted on by groups of politicians in a legislature, such as a parliament or congress, elected (chosen) by the governed peoples. Countries today have a constitution for the overall framework of society and make further laws as needed for matters of detail. Members of society generally have enough freedom within all the legal things they can choose to do. An activity is illegal if it breaks a law or does not follow the laws.

A legal code is a written code of laws that are enforced. This may deal with things like police, courts, or punishments. A lawyer, jurist or attorney is a professional who studies and argues the rules of law. In the United States, there are two kinds of attorneys - "transactional" attorneys who write contracts and "litigators" who go to court. In the United Kingdom, these professionals are called solicitors and barristers respectively.

The Rule of Law is the law which says that government can only legally use its power in a way the government and the people agree on. It limits the powers a government has, as agreed in a country's constitution. The Rule of Law prevents dictatorship and protects the rights of the people. When leaders enforce the legal code honestly, even on themselves and their friends, this is an example of the rule of law being followed. "The rule of law", wrote the ancient Greek philosopher Aristotle in 350 BC, "is better than the rule of any individual."

Culture is usually a major source of the principles behind many laws, and people also tend to trust the ideas based on family and social habits. In many countries throughout history, religion and religious books like the Vedas, Bible or the Koran have been a major source of law.

Types of law
Medical law is the body of laws concerning the rights and responsibilities of medical professionals and their patients. The main areas of focus for medical law include confidentiality, negligence and other torts related to medical treatment (especially medical malpractice), and criminal law and ethics.
Physician-Patient Privilege protects the patient's private conversations with a medical physician (doctor), this also extends to their personal information (like their contact details) shared with medical personnel.
 Property law states the rights and obligations that a person has when they buy, sell, or rent homes and land (called real property or realty), and objects (called personal property).
 Intellectual property (IP) law involves the rights people have over things they create, such as art, music, and literature. This is called copyright. It also protects inventions that people make, by a kind of law called patent. It also covers the rights people have to the names of a company or a distinctive mark or logo. This is called trademark.
 Trust law (business Law) sets out the rules for money that is put into an investment, such as pension funds that people save up for their retirement. It involves many different types of law, including administrative and property law.
Tort law helps people to make claims for compensation (repayment) when someone hurts them or hurts their property.
Criminal law is used by the government to prevent people from breaking laws, and punish people who do break them.
Constitutional law deals with the important rights of the government, and its relationship with the people. It mainly involves the interpretation of a constitution, including things like the Separation of powers of the different branches of government.
A court order is an official proclamation by a judge that defines and authorizes the carrying out of certain steps for one or more parties to a case.
Administrative law is used by ordinary citizens who want to challenge decisions made by governments. It also involves things like regulations, and the operation of the administrative agencies.
International law is used to set out rules on how countries can act in areas such as trade, the environment, or military action. The Geneva Conventions on the conduct of war and the Roerich Pact are examples of international law.
Custom and tradition are practices that are widely adopted and agreed upon in a society, thought often not in a written form. Custom and tradition can be enforced in courts and are sometimes considered as part of the legal reasoning in matters decided in courts. In some societies and cultures all law is or was custom and tradition, though this is increasingly rare although there are some parts of the world where custom tradition are still binding or even the predominant form of law, for example tribal lands or failed states.

Civil law and common law
Civil law is the legal system used in most countries around the world today. Civil law is based on legislation that is found in constitutions or statutes passed by government. The secondary part of civil law is the legal approaches that are part of custom. In civil law governments, judges do not generally have much power, and most of the laws and legal precedent are created by Members of Parliament.

Common law is based on the decisions made by judges in past court cases. It comes from England and it became part of almost every country that once belonged to the British Empire, except Malta, Scotland, the U.S. state of Louisiana, and the Canadian province of Quebec. It is also the predominant form of law in the United States, where many laws called statutes are written by Congress, but many more legal rules exist from the decisions of the courts. Common law had its beginnings in the Middle Ages, when King John was forced by his barons to sign a document called the Magna Carta.

Religious law
Religious law is law based on religious beliefs or books. Examples include the Jewish Halakha, Islamic Sharia, and Christian Canon law.

Until the 1700s, Sharia law was the main legal system throughout the Muslim world. In some Muslim countries such as Saudi Arabia and Iran, the whole legal systems still base their law on Sharia law. Islamic law is often criticised because it often has harsh penalties for crimes. A serious criticism is the judgement of the European Court that "sharia is incompatible with the fundamental principles of democracy".

The Turkish Refah Party's sharia-based "plurality of legal systems, grounded on religion" was ruled to contravene the European Convention for the Protection of Human Rights and Fundamental Freedoms. The Court decided Refah's plan would "do away with the State's role as the guarantor of individual rights and freedoms" and "infringe the principle of non-discrimination between individuals as regards their enjoyment of public freedoms, which is one of the fundamental principles of democracy".

History of law
The history of law is closely connected to the development of human civilizations. Ancient Egyptian law developed in 3000 BC. In 1760 BC King Hammurabi, took ancient Babylonian law and organized it, and had it chiseled in stone for the public to see in the marketplace. These laws became known as the Code of Hammurabi.

The Torah from the Old Testament is an old body of law. It was written around 1280 BC. It has moral rules such as the Ten Commandments, which tell people what things are not permitted. Sometimes people try to change the law. For example, if prostitution is illegal, they try to make it legal.

Legislature
In democracies, the people in a country usually choose people called politicians to represent them in a legislature. Examples of legislatures include the Houses of Parliament in London, the Congress in Washington, D.C., the Bundestag in Berlin, the Duma in Moscow and the Assemblée nationale in Paris. Most legislatures have two chambers or houses, a 'lower house' and an 'upper house'. To pass legislation, a majority of Members of Parliament must vote for a bill in each house. The legislature is the branch of government that writes laws, and votes on whether they will be approved.

Judiciary
The judiciary is a group of judges who resolve people's disputes and determine whether people who are charged with crimes are guilty. In some jurisdictions the judge does not find guilt or innocence but instead directs a jury, how to interpret facts from a legal perspective, but the jury determines the facts based on evidence presented to them and finds the guilt or innocences of the charged person.  Most countries of common law and civil law systems have a system of appeals courts, up to a supreme authority such as the Supreme Court or the High Court. The highest courts usually have the power to remove laws that are unconstitutional (which go against the constitution).

Executive (government) and Head of State
The executive is the governing center of political authority. In most democratic countries, the executive is elected from people who are in the legislature. This group of elected people is called the cabinet. In France, the US and Russia, the executive branch has a President which exists separately from the legislature.

The executive suggests new laws and deals with other countries. As well, the executive usually controls the military, the police, and the bureaucracy. The executive selects ministers, or secretaries of state to control departments such as the health department or the department of justice.

In many jurisdictions the Head of State does not take part in the day-to-day governance of the jurisdiction and takes a largely ceremonial role. This is the case in many Commonwealth nations where the Head of State, usually a Governor almost exclusively acts "on the advice" of the head of the Executive (e.g. the Prime Minister, First Minister or Premier). The primary legal role of the Head of State in these jurisdictions is to act as a check or balance against the Executive, as the Head of State has the rarely exercised power to dissolve the legislature, call elections and dismiss ministers.

Other parts of the legal system
The police enforce the criminal laws by arresting people suspected of breaking the law. Bureaucrats are the government workers and government organizations that do work for the government. Bureaucrats work within a system of rules, and they make their decisions in writing.

Lawyers are people who have learned about laws. Lawyers give people advice about their legal rights and duties and represent people in court. To become a lawyer, a person has to complete a two- or three-year university program at a law school and pass an entrance examination. Lawyers work in law firms, for the government, for companies, or by themselves.

Civil society is the people and groups that are not part of government that try to protect people against human rights abuses and try to protect freedom of speech and other individual rights. Organizations that are part of civil society include political parties, debating clubs, trade unions, human rights organizations, newspapers and charities.

"Corporations are among the organizations that use the legal system to further their goals.  Like the others, they use means such as campaign donations and advertising to persuade people that they are right.  Corporations also engage in commerce and make new things such as automobiles, vaporisers/e-cigarettes, and Unmanned aerial vehicles (i.e. "drones") that the old laws are not well equipped to deal with. Corporations also makes use of a set of rules and regulations to ensure their employees remain loyal to them (usually presented in a legal contract), and that any disobedience towards these rules are considered uncivilized and therefore given grounds for immediate dismissal.

Related pages
Constitution
Death penalty
Ethics
Legal code
Legal rights
Parliament
 Physical law
 Political economy

Further reading
H.L.A. Hart, The Concept of Law, (Penelope A. Bullock & Joseph Raz eds. 2nd ed. 1994) (1961).
Sandro Nielsen: The Bilingual LSP Dictionary. Principles and Practice for Legal Language. Benjamins 1994.
A Companion to Contemporary Political Philosophy. edited by Robert E. Goodin and Philip Pettit. .
Johnson, Alan (1995). The Blackwell Dictionary of Sociology. Blackwells publishers. .
Handbook of Political Institutions. edited by R. A. W. Rhodes, Sarah A. Binder and Bert A. Rockman. Oxford University Press.
An Introduction to IP Law. edited by John Watts. Oxford University Press. Available at Patent Professionals LLC

References

Other websites
 Law -Citizendium

Law


William George Armstrong, 1st Baron Armstrong,  (26 November 1810 – 27 December 1900) was an English engineer and industrialist who founded the Armstrong Whitworth manufacturing concern on Tyneside. He was also an eminent scientist, inventor and philanthropist. In collaboration with the architect Richard Norman Shaw, he built Cragside in Northumberland, the first house in the world to be lit by hydroelectricity. He is regarded as the inventor of modern artillery.

Armstrong was knighted in 1859 after giving his gun patents to the government. In 1887, in Queen Victoria's golden jubilee year, he was raised to the peerage as Baron Armstrong of Cragside.

Early life

Armstrong was born in Newcastle upon Tyne at 9 Pleasant Row, Shieldfield, about a mile from the city centre. Although the house in which he was born no longer exists, an inscribed granite tablet marks the site where it stood. At that time the area, next to the Pandon Dene, was rural. His father, also called William, was a corn merchant on the Newcastle quayside, who rose through the ranks of Newcastle society to become mayor of the town in 1850. An elder sister, Anne, born in 1802, was named after his mother, the daughter of Addison Potter.

Armstrong was educated at the Royal Grammar School, Newcastle upon Tyne, until he was sixteen, when he was sent to Bishop Auckland Grammar School. While there, he often visited the nearby engineering works of William Ramshaw. During his visits he met his future wife, Ramshaw's daughter Margaret, six years his senior.

Armstrong's father was set on his following a career in the law, and so he was articled to Armorer Donkin, a solicitor friend of his father's. He spent five years in London studying law and returned to Newcastle in 1833. In 1835 he became a partner in Donkin's business and the firm became Donkin, Stable and Armstrong. Armstrong married Margaret Ramshaw in 1835, and they built a house in Jesmond Dene, on the eastern edge of Newcastle. Armstrong worked for eleven years as a solicitor, but during his spare time he showed great interest in engineering, developing the "Armstrong Hydroelectric Machine" between 1840 and 1842. In 1837, he laid the foundations for the engineering and environmental consultancy which is today known as Wardell Armstrong.

Change of career
Armstrong was a very keen angler, and while fishing on the River Dee at Dentdale in the Pennines, he saw a waterwheel in action, supplying power to a marble quarry. It struck Armstrong that much of the available power was being wasted. When he returned to Newcastle, he designed a rotary engine powered by water, and this was built in the High Bridge works of his friend Henry Watson. Unfortunately, little interest was shown in the engine. Armstrong subsequently developed a piston engine instead of a rotary one and decided that it might be suitable for driving a hydraulic crane. In 1846 his work as an amateur scientist was recognized when he was elected a Fellow of the Royal Society.

In 1845 a scheme was set in motion to provide piped water from distant reservoirs to the households of Newcastle. Armstrong was involved in this scheme and he proposed to Newcastle Corporation that the excess water pressure in the lower part of town could be used to power a quayside crane specially adapted by himself. He claimed that his hydraulic crane could unload ships faster and more cheaply than conventional cranes. The Corporation agreed to his suggestion, and the experiment proved so successful that three more hydraulic cranes were installed on the Quayside.

The success of his hydraulic crane led Armstrong to consider setting up a business to manufacture cranes and other hydraulic equipment. He therefore resigned from his legal practice. Donkin, his legal colleague, supported him in his career move, providing financial backing for the new venture. In 1847 the firm of W. G. Armstrong & Company bought  of land alongside the river at Elswick, near Newcastle, and began to build a factory there. The new company received orders for hydraulic cranes from Edinburgh and Northern Railways and from Liverpool Docks, as well as for hydraulic machinery for dock gates in Grimsby. The company soon began to expand. In 1850 the company produced 45 cranes and two years later, 75. It averaged 100 cranes per year for the rest of the century. In 1850 over 300 men were employed at the works, but by 1863 this had risen to 3,800. The company soon branched out into bridge building, one of the first orders being for the Inverness Bridge, completed in 1855.

Hydraulic accumulator

Armstrong was responsible for developing the hydraulic accumulator. Where water pressure was not available on site for the use of hydraulic cranes, Armstrong often built high water towers to provide a supply of water at pressure - for instance, the  Grimsby Dock Tower. However, when supplying cranes for use at New Holland on the Humber Estuary, he was unable to do this because the foundations consisted of sand. After much careful thought he produced the weighted accumulator, a cast-iron cylinder fitted with a plunger supporting a very heavy weight. The plunger would slowly be raised, drawing in water, until the downward force of the weight was sufficient to force the water below it into pipes at great pressure. The accumulator was a very significant, if unspectacular, invention, which found many applications in the following years.

Armaments

In 1854, during the Crimean War, Armstrong read about the difficulties the British Army experienced in manoeuvring its heavy field guns. He decided to design a lighter, more mobile field gun, with greater range and accuracy. He built a breech-loading gun with a strong, rifled barrel made from wrought iron wrapped around a steel inner lining, designed to fire a shell rather than a ball. In 1855 he had a five-pounder ready for inspection by a government committee. The gun proved successful in trials, but the committee thought a higher calibre gun was needed, so Armstrong built an 18-pounder on the same design.

After trials, this gun was declared to be superior to all its rivals. Armstrong surrendered the patent for the gun to the British government, rather than profit from its design. As a result he was created a Knight Bachelor and in 1859 was presented to Queen Victoria. Armstrong became employed as Engineer of Rifled Ordnance to the War Department. In order to avoid a conflict of interests if his own company were to manufacture armaments, Armstrong created a separate company, called Elswick Ordnance Company, in which he had no financial involvement. The new company agreed to manufacture armaments for the British government and no other. Under his new position, Armstrong worked to bring the old Woolwich Arsenal up to date so that it could build guns designed at Elswick.

However, just when it looked as if the new gun was about to become a great success, a great deal of opposition to the gun arose, both inside the army and from rival arms manufacturers, particularly Joseph Whitworth of Manchester. Stories were publicised that the new gun was too difficult to use, that it was too expensive, that it was dangerous to use, that it frequently needed repair and so on. All of this smacked of a concerted campaign against Armstrong. Armstrong was able to refute all of these claims in front of various government committees, but he found the constant criticism very wearying and depressing. In 1862 the government decided to stop ordering the new gun and return to muzzle loaders. Also, because of a drop in demand, future orders for guns would be supplied from Woolwich, leaving Elswick without new business. Compensation was eventually agreed with the government for the loss of business to the company, which went on legitimately to sell its products to foreign powers. Speculation that guns were sold to both sides in the American Civil War was unfounded.

Warships

In 1864 the two companies, W. G. Armstrong & Company and Elswick Ordnance Company merged to form Sir W. G. Armstrong & Company. Armstrong had resigned from his employment with the War Office, so there was no longer a conflict of interest. The company turned its attention to naval guns. In 1867 Armstrong reached an agreement with Charles Mitchell, a shipbuilder in Low Walker, whereby Mitchells would build warships and Elswick would provide the guns. The first ship, in 1868 was HMS Staunch, a gunboat.

In 1876, because the 18th-century bridge at Newcastle restricted access by ships to the Elswick works, Armstrong's company paid for a new Swing Bridge to be built, so that warships could have their guns fitted at Elswick. In 1882 Armstrong's company merged with Mitchell's to form Sir William Armstrong, Mitchell and Co. Ltd. and in 1884 a shipyard opened at Elswick to specialise in warship production. The first vessels produced were the torpedo cruisers Panther and Leopard for the Austro-Hungarian Navy. The first battleship produced at Elswick was HMS Victoria, launched in 1887. The ship was originally to be named Renown, but the name was changed in honour of the Queen's Golden Jubilee. Armstrong drove the first and last rivets. The ship was ill-fated, as she was involved in a collision with HMS Camperdown just six years later in 1893 and sank with the loss of 358 men, including Vice-Admiral Sir George Tryon. An important customer of the Elswick yard was Japan, which took several cruisers, some of which defeated the Russian fleet at the Battle of Tsushima in 1905. It was claimed that every Japanese gun used in the battle had been provided by Elswick. Elswick was the only factory in the world that could build a battleship and arm it completely.

The Elswick works continued to prosper, and by 1870 stretched for three-quarters of a mile along the riverside. The population of Elswick, which had been 3,539 in 1851, had increased to 27,800 by 1871. In 1894, Elswick built and installed the steam-driven pumping engines, hydraulic accumulators and hydraulic pumping engines to operate London's Tower Bridge. In 1897 the company merged with the company of Armstrong's old rival, Joseph Whitworth, and became Sir W. G. Armstrong, Whitworth & Co Ltd. Whitworth was by this time dead.

Armstrong gathered many excellent engineers at Elswick. Notable among them were Andrew Noble and George Wightwick Rendel, whose design of gun-mountings and hydraulic control of gun-turrets were adopted worldwide. Rendel introduced the cruiser as a naval vessel. There was great rivalry and dislike between Noble and Rendel, which became open after Armstrong's death.

Cragside

From 1863 onwards, although Armstrong remained the head of his company, he became less involved in its day-to-day running. He appointed several very able men to senior positions and they continued his work. When he married, he acquired a house called Jesmond Dean (sic), which is now demolished, and not to be confused with the nearby Jesmond Dene House. Armstrong's house was to the west of Jesmond Dene, Newcastle, and thus not far from his birthplace, and he began to landscape and improve land that he bought within the Dene. In 1860 he paid local architect John Dobson to design a Banqueting Hall overlooking the Dene, which still survives, though it is now roofless. His house close to Newcastle was convenient for his practice as a solicitor and his work as an industrialist, but when he had more spare time he longed for a house in the country.

He had often visited Rothbury as a child, when he was afflicted by a severe cough, and he had fond memories of the area. In 1863 he bought some land in a steep-sided, narrow valley where the Debdon Burn flows towards the River Coquet near Rothbury. He had the land cleared and supervised the building of a house perched on a ledge of rock, overlooking the burn. He also supervised a programme of planting trees and mosses so as to cover the rocky hillside with vegetation.

His new house was called Cragside, and over the years Armstrong added to the Cragside estate. Eventually the estate was  and had seven million trees planted, together with five artificial lakes and  of carriage drives. The lakes were used to generate hydro-electricity, and the house was the first in the world to be lit by hydro-electricity, using incandescent lamps provided by the inventor Joseph Swan.

As Armstrong spent less and less time at the Elswick works, he spent more and more time at Cragside, and it became his main home. In 1869 he commissioned the celebrated architect Richard Norman Shaw to enlarge and improve the house, and this was done over a period of 15 years. In 1883 Armstrong gave Jesmond Dene, together with its banqueting hall to the city of Newcastle. He retained his house next to the Dene. Armstrong entertained several eminent guests at Cragside, including the Shah of Persia, the King of Siam, the prime minister of China and the Prince and Princess of Wales.

Later life

In 1873 he served as High Sheriff of Northumberland. He was President of the North of England Institute of Mining and Mechanical Engineers from 1872 to 1875. He was elected as the president of the Institution of Civil Engineers in December 1881 and served in that capacity for the next year. He was conferred with Honorary Membership of the Institution of Engineers and Shipbuilders in Scotland in 1884. In 1886, he was persuaded to stand as a Unionist Liberal candidate for Newcastle, but was unsuccessful, coming third in the election. That same year he was presented with the Freedom of the City of Newcastle. In 1887 he was raised to the peerage as Baron Armstrong, of Cragside in the County of Northumberland. His last great project, begun in 1894, was the purchase and restoration of the huge Bamburgh Castle on the Northumberland coast, which remains in the hands of the Armstrong family. His wife, Margaret, died in September 1893, at their house in Jesmond. Armstrong died at Cragside on 27 December 1900, aged ninety. He was buried in Rothbury churchyard, alongside his wife. The couple had no children, and Armstrong's heir was his great-nephew William Watson-Armstrong. He was succeeded as chairman of the company by his one-time protégé, Andrew Noble.

Such was Armstrong's fame as a gun-maker that he is thought to be a possible model for George Bernard Shaw's arms magnate in Major Barbara. The title character in Iain Pears' historical-mystery novel Stone's Fall also has similarities to Armstrong.

His attitude to armaments
There is no evidence that Armstrong agonised over his decision to go into armament production. He once said: "If I thought that war would be fomented, or the interests of humanity suffer, by what I have done, I would greatly regret it. I have no such apprehension."  He also said: "It is our province, as engineers to make the forces of matter obedient to the will of man; those who use the means we supply must be responsible for their legitimate application."

Views on renewable energy

Armstrong advocated the use of renewable energy. Stating that coal "was used wastefully and extravagantly in all its applications", he predicted in 1863 that Britain would cease to produce coal within two centuries. As well as advocating the use of hydroelectricity, he also supported solar power, stating that the amount of solar energy received by an area of  in the tropics would "exert the amazing power of 4,000 horses acting for nearly nine hours every day".

The benefactor
Armstrong donated the long wooded gorge of Jesmond Dene to the people of the city of Newcastle upon Tyne in 1883, as well as Armstrong Bridge and Armstrong Park nearby. He was involved in the foundation in 1871 of the College of Physical Science  - a  forerunner of the University of Newcastle, renamed Armstrong College in 1906. He was President of the Literary and Philosophical Society of Newcastle upon Tyne from 1860 until his death, as well as twice president of the Institution of Mechanical Engineers. Armstrong gave £11,500 towards the building of Newcastle's Hancock Natural History Museum, which was completed in 1882. This sum is equivalent to over £555,000 in 2010. Lord Armstrong's generosity extended beyond his death. In 1901 his heir, William Watson-Armstrong gave £100,000 (equivalent to £ in ), for the building of the new Royal Victoria Infirmary in Newcastle upon Tyne. Its original 1753 building at Forth Banks near the River Tyne was inadequate and impossible to expand. In 1903 the barony of Armstrong was revived in favour of William Watson-Armstrong.

Honours
 In 1846 he was made a Fellow of the Royal Society (FRS).
 In 1850 he received the Telford Medal from the Institution of Civil Engineers.
 In 1859 William Armstrong was knighted as a Knight Bachelor (Kt).
 He was made a Companion of the Order of the Bath in the Civil Division
 In 1878 he received the Albert Medal from the Royal Society of Arts.
 In 1886 he was awarded the Freedom of the City of Newcastle.
 In 1887 he was raised to the peerage as a Hereditary peer, allowing him to sit in the House of Lords. He took the title Baron Armstrong, of Cragside in the County of Northumberland.
 In 1891 he received the Bessemer Gold Medal from the Iron and Steel Institute.

Honorary Degrees

Arms

Publications

, Plates: 17–24

References

Further reading

 Heald, Henrietta (2012), William Armstrong: Magician of the North. Alnwick, Northumberland: McNidder & Grace. .
 Smith, Ken (2005), Emperor of Industry: Lord Armstrong of Cragside. Newcastle: Tyne Bridge Publishing, 48 pp. .
 Bastable, Marshall J. (2004), Arms and the State, Sir William Armstrong and the Remaking of British Naval Power. UK: Ashgate, 300 pp. .

External links

 William Armstrong website

1810 births
1900 deaths
People from Newcastle upon Tyne
People from Rothbury
People educated at the Royal Grammar School, Newcastle upon Tyne
Barons Armstrong
Companions of the Order of the Bath
English industrialists
English engineers
English inventors
Fellows of the Royal Society
History of Northumberland
Hydraulic engineers
Knights Bachelor
People associated with Newcastle University
Presidents of the Institution of Civil Engineers
Weapon designers
High Sheriffs of Northumberland
Mayors of Newcastle upon Tyne
Liberal Unionist Party parliamentary candidates
Bessemer Gold Medal
19th-century English lawyers
Peers of the United Kingdom created by Queen Victoria
19th-century English businesspeople

William Armstrong, 1st Baron Armstrong


Feldspar is the name of a group of rock-forming tectosilicate minerals that make up as much as 60% of the Earth's crust.

Feldspar forms crystals from magma in both intrusive and extrusive rocks, and they can also happen as compact minerals, as veins, and are also present in many types of metamorphic rock. Rock formed entirely of plagioclase feldspar is known as anorthosite. Feldspar is also found in many types of sedimentary rock.

Feldspar is typically reddish or pale pink in color, and has a hardness of 6 on the Mohs scale, making it roughly as hard to scratch as glass.

There are two groups of feldspar, both made out of silica and aluminum:
Orthoclase or "alkali" feldspars: a group of minerals that all have the same formula (KAlSi3O8 with sodium sometimes replacing the potassium in some pieces), but are formed in different ways because of how different the times and places where they formed were.
Plagioclase feldspars: A series of minerals that are made up of a series of two chemicals (Albite, NaAlSi3O8, and anorthite CaAl2Si2O8), with a given piece having its place on the series determined by the relative amounts of the two chemicals.

Minerals

Feldspar


For the calendar of religious holidays and periods, see liturgical year.

গ্রেগরিয়ান পাঞ্জী (ইংরেজী: Gregorian calendar বুলতারা পাঞ্জী এহান পৃথিবীর হাব্বি দেশে চলের বুললেউ য়্যাকরের। এহান জুলিয়ান পাঞ্জীত্ত পতিয়া হঙকরিসিহান যেহান পয়লাকা কালাব্রিয়ান ডক্টর আলইয়াস লিলিয়াসে প্রস্তাব করিয়া বারো চালেইলতা পোপ গ্রেগরি ত্রয়োদশে যেগর নাংহান ইলয়া এহানর নাংহান থনা ইল। ফেব্রুয়ারী ২৪ ১৫৮২ খ্রীস্টাব্দত্ত চলানি অকরলো। অতাইলেউ তিলপারাজ্য বারো সময়অহানর ব্রিটিশ কলোনী বুলিয়া তিলপারাষ্টত এহান চলিলতা ১৭৫২ খ্রীস্টাব্দত্ত। ইউরোপর আবকচা দেশ, যেসাদে রাশিয়াত ১৮১৯ খ্রীস্টাব্দ পেয়া এহান চলিয়া আহিসিল। এহানর মারি এতা রুহিহান ইয়া যিশু খ্রীষ্টর জরমর সময় অহানাত্ত গনানি অকরলা যেহানরে "আন্ন ডমিনি" এরা বুলতারা।

The Gregorian Calendar was devised both because the mean year in the Julian Calendar was slightly too long, causing the vernal equinox to slowly drift backwards in the calendar year, and because the lunar calendar used to compute the date of Easter had grown conspicuously in error as well.

The Gregorian calendar system dealt with these problems by dropping a certain number of days to bring the calendar back into synchronization with the seasons, and then slightly shortening the average number of days in a calendar year, by omitting three Julian leap-days every 400 years.

সালকরিয়া

The Gregorian solar calendar is an arithmetical calendar. It counts days as the basic unit of time, grouping them into years of 365 or 366 days. The solar calendar repeats completely every 146,097 days, which fill 400 years, and which also happens to be 20871 seven-day weeks. Of these 400 years, 303 (the "common years") have 365 days, and 97 - the leap years - have 366 days. This gives an average year length of exactly 365.2425 days - or 365 days, 5 hours, 49 minutes and 12 seconds.

A Gregorian year is divided into twelve months of irregular length (but note that there is a period of 153 days divided over 5 months in an alternating pattern from March to July that repeats from August to December):

A calendar date is fully specified by the year (numbered by some scheme beyond the scope of the calendar itself), the month (identified by name or number), and the day of the month (numbered sequentially starting at 1).

Leap years are all years divisible by 4, with the exception of those divisible by 100, but not by 400. These 366-day years add a 29th day to February, which normally has 28 days. Thus, the essential ongoing differential feature of the Gregorian calendar, as opposed to the Julian calendar, is that the Gregorian omits 3 leap days every 400 years. This difference would have been more noticeable in modern memory, were it not for the fact that the year 2000 was a leap year in both the Julian and Gregorian calendar systems.

The intercalary day in a leap year is known as a leap day. Since Roman times 24 February (bissextile) was counted as the leap day, but nowadays 29 February is regarded as the leap day in most countries.

Although the calendar year runs from 1 January to 31 December, sometimes year numbers were based on a different starting point within the calendar. Confusingly, the term "Anno Domini" is not specific on this point, and actually refers to a family of year numbering systems with different starting points for the years. See the section below for more discussion of this issue.

ইতিহাসহান

হংকরানি
The motivation of the Catholic Church in adjusting the calendar was to have Easter celebrated at the time that they thought had been agreed to at the First Council of Nicaea in 325. Although a canon of the council implies that all churches used the same Easter, they did not. The Church of Alexandria celebrated Easter on the Sunday after the 14th day of the Moon that falls on or after the vernal equinox, which they placed on 21 March. However, the Church of Rome still regarded 25 March as the equinox and used a different day of the moon. By the tenth century all churches (except for some on the eastern border of the Byzantine Empire) had adopted the Alexandrian Easter, which still placed the vernal equinox on 21 March, although Bede had already noted its drift in 725—it had drifted even further by the sixteenth century.

Worse, the reckoned Moon that was used to compute Easter was fixed to the Julian year by a 19 year cycle. However, that approximation built up an error of one day every 310 years, so by the sixteenth century the lunar calendar was out of phase with the real Moon by four days.

The Council of Trent approved a plan in 1563 for correcting the calendrical errors, requiring that the date of the vernal equinox be restored to that which it held at the time of the First Council of Nicaea in 325 and that an alteration to the calendar be designed to prevent future drift. This would allow for a more consistent and accurate scheduling of the feast of Easter.

The fix was to come in two stages. First, it was necessary to approximate the correct length of a solar year. The value chosen was 365.2425 days in decimal notation. This is 365;14,33 days in sexagesimal notation—the length of the tropical year, rounded to two sexagesimal positions; this was the value used in the major astronomical tables of the day. Although close to the mean tropical year of 365.24219 days, it is even closer to the vernal equinox year of 365.2424 days; this fact made the choice of approximation particularly appropriate as the purpose of creating the calendar was to ensure that the vernal equinox would be near a specific date (21 March). See Accuracy.

The second stage was to devise a model based on the approximation which would provide an accurate yet simple, rule-based calendar. The formula designed by Aloysius Lilius was ultimately successful. It proposed a 10-day correction to revert the drift since Nicaea, and the imposition of a leap day in only 97 years in 400 rather than in 1 year in 4. To implement the model, it was provided that years divisible by 100 would be leap years only if they were divisible by 400 as well. So, in the last millennium, 1600 and 2000 were leap years, but 1700, 1800 and 1900 were not. In this millennium, 2100, 2200, 2300 and 2500 will not be leap years, but 2400 will be. This theory was expanded upon by Christopher Clavius in a closely argued, 800 page volume. He would later defend his and Lilius's work against detractors.

The 19-year cycle used for the lunar calendar was also to be corrected by one day every 300 or 400 years (8 times in 2500 years) along with corrections for the years (1700, 1800, 1900, 2100 et cetera) that are no longer leap years. In fact, a new method for computing the date of Easter was introduced.

Lilius originally proposed that the 10-day correction should be implemented by deleting the Julian leap day on each of its ten occurrences during a period of 40 years, thereby providing for a gradual return of the equinox to 21 March. However, Clavius's opinion was that the correction should take place in one move and it was this advice which prevailed with Gregory. Accordingly, when the new calendar was put in use, the error accumulated in the 13 centuries since the Council of Nicaea was corrected by a deletion of ten days. The last day of the Julian calendar was Thursday 4 October 1582 and this was followed by the first day of the Gregorian calendar, Friday 15 October 1582 (the cycle of weekdays was not affected). Nevertheless, the dates "5 October 1582" to "14 October 1582" (inclusive) are still valid in virtually all countries because even most Roman Catholic countries did not adopt the new calendar on the date specified by the bull, but months or even years later (the last in 1587).

মারির অকরানিহান
During the Middle Ages 1 January was given the name New Year's Day (or an equivalent name) in all Western European countries (those with predominantly Catholic populations), even while most of those countries began their numbered year on 25 December (the Nativity of Jesus), then 25 March (the Incarnation of Jesus), and even Easter, as in France. This name was the result of always displaying the months of the medieval calendar from January to December (in twelve columns containing 28 to 31 days each), just like the Romans did. Furthermore, all Western European countries (except for a few Italian states) shifted the first day of their numbered year to 1 January while they were still using the Julian calendar, before they adopted the Gregorian calendar, many during the sixteenth century. Eastern European countries (most of them with populations showing allegiance to the Orthodox Church) began their numbered year on 1 September (since about 988). The following list is partially based on Old Style and New Style Dates and The Change of New Year's Day.

Neither the papal bull nor its attached canons explicitly state that the year of the Gregorian calendar is to begin on 1 January, contrary to popular opinion. However, it does imply such a year by including two tables of saint's days, one labeled 1582 which ends on 31 December, and another for any full year that begins on 1 January. It also specifies its epact relative to 1 January, in contrast with the Julian calendar, which specified it relative to 22 March. These would have been the inevitable result of the above shift in the beginning of the Julian year.

During the period between 1582, when the first countries adopted the Gregorian calendar, and 1923, when the last European country adopted it, it was often necessary to indicate the date of some event in both the Julian calendar and in the Gregorian calendar, for example, "10/21 February 1751/52", where the dual year accounts for some countries already beginning their numbered year on 1 January while others were still using some other date. Even before 1582, the year sometimes had to be double dated because of the different beginnings of the year in various countries. Woolley, writing in his biography of John Dee (1527-1608/9), notes that immediately after 1582 English letter writers "customarily" used "two dates" on their letters, one OS and one NS.

রোমান ক্যথলিকর বারেদে য়্যাকরানি

Only Spain and her territories, Portugal, the Polish-Lithuanian Commonwealth, and most of Italy implemented the new calendar on Friday, 15 October 1582, following Julian Thursday, 4 October 1582. France adopted the new calendar on Monday, 20 December 1582, following Sunday, 9 December 1582. The Protestant Dutch provinces of Holland and Zeeland also adopted it in December of that year.

Most non-Catholic countries initially objected to adopting a Catholic invention. England, Scotland and thereby the rest of the British Empire (including the eastern part of what is now the United States) did not adopt the Gregorian calendar until 1752; by which time it was necessary to correct by eleven days (Wednesday, 2 September 1752 being followed by Thursday, 14 September 1752) to account for 29 February 1700 (Julian). A few years later, when the son of the Earl of Macclesfield (who had been influential in passing the calendar law) ran for a seat in Parliament in Oxfordshire as a Whig in 1754, dissatisfaction with the calendar reforms was one of a number of issues raised by his Tory opponents. In 1755, William Hogarth made a painting (and an engraved print from the painting) loosely based on these elections, in which the campaign slogan "Give us our Eleven Days" appears (on floor at lower right); this was later misunderstood, giving rise to apocryphal stories of widespread riots at the change-over.

Great Britain legislated special provisions to make sure that monthly or yearly payments would not become due until the dates that they originally would have in the Julian calendar. From 1753 until 1799, the tax year in Great Britain began on 5 April, which was the "old style" new year of 25 March. A 12th skipped Julian leap day in 1800 changed its start to 6 April. It was not changed when a 13th Julian leap day was skipped in 1900, so the tax year in the United Kingdom is still 6 April.

"Old Style" (OS) and "New Style" (NS) are sometimes added to dates to identify which system is used in the British Empire and other countries that did not immediately change. In Britain it is usual to map most dates from the Julian year onto the Gregorian year without converting the day and month. But because the start of the year did not change until the same year that the Gregorian calendar was introduced, OS/NS is particularly relevant for dates which fall between 1 January and 25 March. For example the execution of King Charles I is usually recorded as having taken place on 30 January 1649 (NS), but in contemporary documents it is recorded as having taken place on 30 January 1648.

Denmark, Norway and the Protestant states of Germany adopted the solar portion of the new calendar on Monday, 1 March 1700,, following Sunday, 18 February 1700, due to the influence of Ole Rømer, but did not adopt the lunar portion. Instead, they decided to calculate the date of Easter astronomically using the instant of the vernal equinox and the full moon according to Kepler's Rudolphine Tables of 1627. They finally adopted the lunar portion of the Gregorian calendar in 1776. The remaining provinces of the Dutch Republic also adopted the Gregorian calendar in 1700.

Sweden's relationship with the Gregorian Calendar had a difficult birth. Sweden started to make the change from the OS calendar and towards the NS calendar in 1700, but it was decided to make the (then 11 day) adjustment gradually, by excluding the leap days (29 February) from each of 11 successive leap years, 1700 to 1740. In the meantime, not only would the Swedish calendar be out of step with both the Julian calendar and the Gregorian calendar for 40 years, but also the difference would not be static but would change every 4 years. This strange system clearly had great potential for endless confusion when working out the dates of Swedish events in this 40 year period. To make matters worse, the system was poorly administered and the leap days that should have been excluded from 1704 and 1708 were not excluded. The Swedish calendar should by now have been 8 days behind the Gregorian, but it was still in fact 10 days behind. King Charles XII wisely recognised that the gradual change to the new system was not working and he abandoned it. However, rather than now proceeding directly to the Gregorian calendar (as in hindsight seems to have been the sensible and obvious thing to do), it was decided to revert to the Julian calendar. This was achieved by introducing the unique date 30 February in the year 1712, adjusting the discrepancy in the calendars from 10 back to 11 days. Sweden finally adopted the Gregorian calendar in 1753, when Wednesday, 17 February was followed by Thursday, 1 March.

In Alaska, the change took place when Friday, October 6, 1867 was followed again by Friday, October 18 after the US purchase of Alaska from Russia, which was still on the Julian calendar. Instead of 12 days, only 11 were skipped, and the day of the week was repeated on successive days, because the International Date Line was shifted from east of to west of Alaska along with the change to the Gregorian calendar.

In Russia the Gregorian calendar was accepted after the October Revolution (so named because it took place in October 1917 in the Julian calendar). On 24 January 1918 the Council of People's Commissars decreed that Wednesday, 31 January 1918 was to be followed by Thursday, 14 February 1918.

The last country of Eastern Europe to adopt the Gregorian calendar was Greece on Thursday, 1 March 1923, following Wednesday, 15 February 1923. However, these were all civil adoptions—none of the national churches accepted it. Instead, a Revised Julian calendar was proposed in May 1923 which dropped 13 days in 1923 and adopted a different leap year rule that resulted in no difference between the two calendars until 2800. The Greek Orthodox church and the churches of Bulgaria, Romania, Poland adopted the Revised Julian calendar, so these New calendarists will celebrate the Nativity along with the Western churches on 25 December in the Gregorian calendar until 2800. The Orthodox churches of Russia, Serbia, Jerusalem, and a few bishops in Greece did not accept the Revised Julian calendar. These Old Calendarists continue to celebrate the Nativity on 25 December in the Julian calendar, which is 7 January in the Gregorian calendar until 2100. All of the other Eastern churches that are not Orthodox churches, like the Coptic, Ethiopic, Nestorian, Jacobite, and Armenian, continue to use their own calendars, which usually result in fixed dates being celebrated in accordance with the Julian calendar. All Eastern churches continue to use the Julian Easter with the sole exception of the Finnish Orthodox Church, which has adopted the Gregorian Easter.

মুং এশিয়াত য়্যাকরানি

The Republic of China (ROC) formally adopted the Gregorian calendar at its founding on 1 January 1912, but China soon descended into a period of warlordism with different warlords using different calendars. With the unification of China under the Kuomintang in October 1928, the Nationalist Government decreed that effective 1 January 1929 the Gregorian calendar would be used henceforth. However, China retained the Chinese traditions of numbering the months and a modified Era System, backdating the first year of the ROC to 1912; this system is still in use in Taiwan where this ROC government retains control. Upon its foundation in 1949, the People's Republic of China continued to use the Gregorian calendar with numbered months, but abolished the ROC Era System and adopted the Western fashion of naming years.

Japan replaced the traditional lunisolar calendar with the Gregorian calendar on 1 January 1873, but, like China, continued to number the months, and used reign names instead of the Common Era: Meiji 1=1868, Taisho 1=1912, Showa 1=1926, Heisei 1=1989, and so on. The "Western calendar" (西暦, seireki) using western year numbers, is also widely accepted by civilians and to a lesser extent by government agencies.

Korea started using the Gregorian calendar on 1 January 1896 due to Japanese influence. The lunisolar Korean calendar used immediately before that day was based on the lunisolar Chinese calendar.

সময়রদুরগ

Proleptic Gregorian calendar

The Gregorian calendar can, for certain purposes, be extended backwards to dates preceding its official introduction, producing the proleptic Gregorian calendar. However, this proleptic calendar should be used with great caution.

For ordinary purposes, the dates of events occurring prior to 15 October 1582 are generally shown as they appeared in the Julian calendar, and not converted into their Gregorian equivalents.

However, events occurring in countries where the Gregorian calendar was introduced later than 4 October 1582 are a little more contentious. For example, in Great Britain and its overseas possessions (then including the American colonies), the new calendar was not introduced until 14 September 1752. How, then, would people date events occurring in Britain and her possessions in the 170 years between 1582 and 1752? The answer depends very much on the context, but writers who want to avoid confusion make it absolutely clear which calendar is being used. People have avoided changing historical records in Britain deriving from this period; however, it is often highly desirable to translate particular Old Style dates into their New Style equivalents, such as where the context includes reference to other countries that had already converted to New Style before Britain did. Astronomers avoid this ambiguity by the use of the Julian day number.

If comparisons of dates are done using different calendars, we can encounter logical absurdities such as William and Mary of Orange seeming to arrive in London to accept the English crown, a week or so before they left the Netherlands; and Shakespeare and Cervantes apparently dying on exactly the same date (23 April 1616), when in fact Cervantes predeceased Shakespeare by 10 days in real time. This coincidence however has allowed UNESCO to make 23 April the World Book and Copyright Day.

For dates before the year 1, unlike the proleptic Gregorian calendar used in the international standard ISO 8601, the traditional proleptic Gregorian calendar (like the Julian calendar) does not have a year 0 and instead uses the ordinal numbers 1, 2, … both for years AD and BC and for CE and BCE. Thus the traditional timeline is 2 BC, 1 BC, AD 1, and AD 2. ISO 8601 uses astronomical year numbering which includes a year 0 and negative numbers before it. Thus the ISO 8601 timeline is -0001, 0000, 0001, and 0002.

Confusion with British versus American usage
Dates of events in Britain prior to 1752 are usually now shown in their original Old Style form, whereas dates of events in (then British) America prior to 1752 are usually now shown in the New Style form.

 For example, Shakespeare died on 23 April (OS), and it is rare to see this converted to 3 May (NS). But while George Washington was born on 11 February (OS), his birthday is now celebrated on 22 February (NS). (He changed its celebration date himself, as a twenty-one-year-old surveyor.)

However, neither of these practices is universal in either country, so it is sometimes very unclear which calendar is being used, and this can lead to false assumptions, which can lead to dates being inaccurately converted from one calendar to the other. Since the resurgence of interest in the history of the calendar, more information about the real dates (according to various calendars) of events has been forthcoming and many previous errors have been corrected. While these changes are welcome, there is still much scope for confusion; therefore, noting the calendar being used in transitional periods would help the reader understand the dates involved.

Difference between Gregorian and Julian calendar dates
Since the introduction of the Gregorian calendar, the difference between faster Gregorian (New Style) and slower Julian (Old Style) calendar dates has increased as follows:

The difference grows by 3 days in every four centuries.

On average, 48,700 Gregorian years and 48,699 Julian years each equal 17,787,309.75 days. Any 194,800 consecutive Gregorian years and any consecutive 194,796 Julian years each have exactly 71,149,239 days. Approximately every 487 centuries, there is a period during which the difference between the calendars is approximately an integral number of years and the day of the year can be the same on both calendars. Every fourth one of these is a period that occurs exactly every 71,149,239 days (194,800 Gregorian years or 194,796 Julian years) and lasts 36,524 days (100 years on Gregorian calendar, and 99 years, 365 days on the Julian calendar), during which the difference between the calendars is an integral multiple of 1,461 days (four years) and the month and day of the month (but not the year) are the same on both calendars for the entire period. The remainder are periods of several centuries each, during which the day of the year coincides for approximately 25–75% of the months in each century.

Months of the year

English speakers sometimes remember the number of days in each month by the use of the traditional mnemonic verse:

Thirty days hath September,
April, June, and November.
All the rest have thirty-one,
excepting February alone,
which hath twenty-eight.
Leap year cometh one year in four,
in which February hath one day more.

(The hath in the first line of the poem is also given as has or have.)

Alternate endings include:

excepting February alone,
which has twenty-eight days or,
in a leap year, adds one more.

which has but twenty-eight, in fine,
till leap year gives it twenty-nine.

which has eight and a score,
until leap year gives it one day more.

which hath twenty-eight days clear,
and twenty-nine in each leap year.

in each leap we assign,
February twenty-nine.

When short February's done,
all the rest have thirty-one.

(except February,)
February alone don't hold the line,
for three years it has twenty-eight,
and the fourth year twenty-nine.

but February, it is done
at twenty-eight, but add one more
whenever the year divides by four.

A language-independent alternative used in many countries is to hold up your two fists with the index knuckle of your left hand against the index knuckle of your right hand. Then, starting with January from the little knuckle of your left hand, count knuckle, space, knuckle, space through the months. A knuckle represents a month of 31 days, and a space represents a short month (a 28- or 29-day February or any 30-day month). The junction between the hands is not counted, so the two index knuckles represent July and August. (The knuckle method also works by starting the sequence on the right hand's index knuckle, and continue afterwards to the left hand's index knuckle.) You can also use just one hand; after counting the fourth knuckle as July, start again counting the first knuckle as August.

The Origins of English naming used by the Gregorian calendar:
 January: Janus (Roman god)
 February: februarius (mensis) (Latin for "month of purification (rituals)", of unknown origin, said to be Sabine word, last month of ancient pre-450 BC Roman calendar)
 March: Mars (Roman god)
 April: (mensis) Aprilis (Latin for "month of Venus", second month of ancient Roman calendar)
 May: Maia Maiestas (Roman goddess)
 June: Juno (Roman goddess)
 July: Julius Caesar (Roman dictator)
 August: Augustus (Roman emperor)
 September: septem (Latin for seven, the seventh month in the calendar of Romulus)
 October: octo (Latin for eight, the eighth month in the calendar of Romulus)
 November: novem (Latin for nine, the ninth month in the calendar of Romulus)
 December: decem (Latin for ten, the tenth month in the calendar of Romulus)

Accuracy
The Gregorian calendar improves the approximation made by the Julian calendar by skipping three Julian leap days in every 400 years, giving an average year of 365.2425 mean solar days long, which has an error of about one day per 3300 years with respect to the mean tropical year of 365.24219 days but less than half this error with respect to the vernal equinox year of 365.24237 days. Both are substantially more accurate than the one day in 128 years error of the Julian calendar (average year 365.25 days).

On timescales of thousands of years, the Gregorian calendar falls behind the seasons drastically because the slowing down of the Earth's rotation makes each day slightly longer over time (see tidal acceleration and leap second) while the year maintains a more uniform duration. The equinox will occur earlier than now by a number of days approximately equal to [years into future/5000]2. This is a problem that the Gregorian calendar shares with any fixed rule-based calendar.

Calendar seasonal error

This image shows the difference between the Gregorian calendar and the seasons.

The y-axis is "days error" and the x-axis is Gregorian calendar years.

Each point represents a single date on a given year. The error shifts by about a quarter of a day per year. Years that are multiples of 100 but not 400 are not leap years. This causes a correction on years 1700, 1800, 1900, 2100, 2200, and 2300.

For instance, these corrections cause 23 December 1903 to be the latest December solstice, and 20 December 2096 to be the earliest solstice—2.25 days of variation compared with the seasonal event.

Numerical facts
When leap years and common years are taken into account, there are a total of 14 possible Gregorian calendars.

When different dates of Easter are also taken into account, there are a total of 70 possible Gregorian calendars.

An average year is 365.2425 days = 52.1775 weeks = 8,765.82 hours = 525,949.2 minutes = 31,556,952 seconds. All these numbers are exact, apart from leap seconds.

A common year is 365 days = 8,760 hours = 525,600 minutes = 31,536,000 seconds.

A leap year is 366 days = 8,784 hours = 527,040 minutes = 31,622,400 seconds.

Since 1971, some years may also contain one or more leap seconds, to account for cumulative irregularities in the Earth's rotation. So far, these have always been positive and have occurred on average once every 18 months.

The day of the year is somewhat inconvenient to compute, not in the least because of the leap day somewhere in the middle; but the calendar has this repeating pattern for the months March through July and August through December: 31, 30, 31, 30, 31 days, totalling 153 days. In fact, any 5 consecutive months not containing February, count 153 days. 153 happens to be the 17th triangular number, and the sum of the first 5 factorials (among other numerical trivia).

See also common year starting on Sunday and dominical letter.

The 400-year cycle of the Gregorian calendar has 146,097 days and hence exactly 20,871 weeks. So, for example, the days of the week in Gregorian 1603 were exactly the same as for 2003. This also causes more months to begin on a Sunday (and hence have Friday 13) than any other day of the week (see below for a more detailed explanation of how this happens). 688 out of every 4800 months (or 172/1200) begin on a Sunday, while only 684 out of every 4800 months (171/1200) begin on each of Saturday and Monday, the least common cases.

A smaller cycle is 28 years (1,461 weeks), provided that there is no dropped leap year in between. Days of the week in years may also repeat after 6, 11, 12, 28 or 40 years. Intervals of 6 and 11 are only possible with common years, while intervals of 28 and 40 are only possible with leap years. An interval of 12 years only occurs with common years when there is a dropped leap year in between.

The Doomsday algorithm is a method by which you can discern which of the 14 calendar variations should be used in any given year (after the Gregorian reformation). It is based on the last day in February, referred to as the Doomsday.

The Gregorian serial date, also called Rata Die, is the number of days from January 1, 1 A.D. (counting that day as day 1). For  , , the serial date is . It is 678576 more than the Modified Julian date, and 1721425 less than the Julian date .

Week
In conjunction with the system of months there is a system of weeks. A physical or electronic calendar provides conversion from a given date to the weekday, and shows multiple dates for a given weekday and month. Calculating the day of the week is not very simple, because of the irregularities in the Gregorian system.

The ISO week date connects Gregorian years and weeks, defining a leap week calendar with so-called "ISO years" deviating at the beginning and end up to 3 days from Gregorian years, and with week numbers by year.

Origins of English naming used by the Gregorian Calendar:

 Monday - moon day (celestial)
 Tuesday - Tyr's day (Old Norse god)
 Wednesday - Woden's day (Old English god)
 Thursday - Thor's day (Old Norse god)
 Friday - Frigg's day (Old Norse goddess) (Friday is often erroneously associated with Freyja)
 Saturday - Saturn's day (Roman god)
 Sunday - sun day (celestial)

Distribution of dates by day of the week
Because there are 97 leap years in every 400 years in the Gregorian Calendar, there are on average 13 for each starting weekday in each cycle. This already shows that the frequency is not the same for each weekday, which is due to the effects of the "common" centennial years (1700, 1800, 1900, 2100, 2200 etc.).

The absence of an extra day in such years causes the following leap year (1704, 1804, 1904, 2104 etc.) to start on the same day of the week as the leap year twelve years before (1692, 1792, 1892, 2092 etc.). Similarly, the leap year eight years after a "common" centennial year (1708, 1808, 1908, 2108 etc.) starts on the same day of the week as the leap year immediately prior to the "common" centennial year (1696, 1796, 1896, 2096 etc.). Thus, those days of the week on which such leap years begin gain an extra year or two in each cycle. In each cycle there are:

 13 leap years starting on Monday
 14 leap years starting on Tuesday
 14 leap years starting on Wednesday
 13 leap years starting on Thursday
 15 leap years starting on Friday
 13 leap years starting on Saturday
 15 leap years starting on Sunday

Note that as a cycle, this pattern is symmetric with respect to the low Saturday value.

A leap year starting on Sunday means the next year does not start on Monday, so more leap years starting on Sunday means less years starting on Monday, etc. Thus the pattern of number of years starting on each day is inverted and shifted by one weekday: 56, 58, 57, 57, 58, 56, 58 (symmetric with respect to the high Sunday value).

The number of common years starting on each day is found by subtraction: 43, 44, 43, 44, 43, 43, 43.

The frequency of a particular date being on a particular weekday can easily be derived from the above (for dates in March and later, relate them to the next New Year).

See also the cycle of Doomsdays.

Days of the week
January 1 of any year whose number is a multiple of 400 is a Saturday. From this you can work out the day of the week of any date.

See also:
 Days of the week
 Calculating the day of the week

Trivia
The Roman calendar was modified by Julius Caesar when he occupied the office of Pontifex Maximus and the Julian calendar was subsequently modified by Gregory XIII, who, as pope, also held the title Pontifex Maximus.

Non-leap years always begin and end on the same day of the week. For example, 2003 began on a Wednesday and ended on a Wednesday. Leap years end on the next day of the week from which they begin. For example, 2004 began on a Thursday and ended on a Friday.

Not counting leap years, any calendar date will move to the next day of the week the following year. For example, if your birthday fell on a Tuesday in 2002, it fell on a Wednesday in 2003. Leap years make things a little more complicated. 2004 was leap year, so calendar days of March 1 or later in the year, moved two days of the week from 2003. However, calendar days occurring before March 1 do not make the extra day of the week jump until the year following a leap year. So, if your birthday is June 15, then it must have fallen on a Sunday in 2003 and a Tuesday in 2004. If, however, your birthday is February 15, then it must have fallen on a Saturday in 2003, a Sunday in 2004 and a Tuesday in 2005.

In any year (even a leap year), July always begins on the same day of the week that April does. Therefore, the only difference between a July calendar page and an April calendar page in the same year is the extra day July has. The same relationship exists between September and December as well as between March and November. Add an extra day to the September page and you've got December. Take a day away from the March page and you've got November. In non-leap years only, there are additional matches: October duplicates January, and March and November duplicate February in their first 28 days. In leap years only, there is a different set of additional matches: July is a duplicate of January while February is duplicated in the first 29 days of August.

Saint Teresa of Ávila died on the night from 4 October to 15 October 1582, that is, exactly when Spain and the Catholic world switched to the Gregorian calendar.

পাসিতা

 Gregorian reform of the calendar: Proceedings of the Vatican conference to commemorate its 400th anniversary, 1582-1992, ed. G. V. Coyne, M. A. Hoskin, and O. Pedersen (Vatican City: Pontifical Academy of Sciences, Specolo Vaticano, 1983).
 The Oxford Companion to the Year. Bonnie Blackburn & Leofranc Holford-Strevens. Oxford University Press 1999. ISBN 0-19-214231-3. Pages 98-99.
 Calendar: Humanity's Epic Struggle To Determine A True And Accurate Year, David Ewing Duncan, Harper Perennial, 1999, ISBN 0-380-79324-5.
 Online Etymology Dictionary retrieved August 23, 2006

Footnotes

External links
 Inter Gravissimas, Gregory XIII's bull introducing the new calendar (Latin and French)
 Inter Gravissimas (Latin and French plus English)
 British Calendar Act 1751
 Frequently Asked Questions about Calendars
 The Perpetual Calendar Gregorian Calendar adoption dates for many countries.
 Synoptical Julian - Gregorian calendar Compare Old and New Style dates 1582 - 2100.
 Gregorian Calendar Printer
 Gregorian Calendar in norwegian, with some norwegian information

Specific calendars
1582 establishments
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Virtue (Latin virtus; Greek ἀρετή) is a kind of behaviour which is thought to be good.  The adjective is "virtuous".  Someone who lives a virtuous life is someone who leads a good moral life, doing things that society thinks are good.  The opposite of virtue is vice.

Philosophers throughout the ages have written their ideas about what they think virtue is.  The Ancient Greek philosophers from Plato onwards said that virtue consisted of four things: Justice, Courage, Wisdom, and Moderation.  In the Christian religion the three virtues  were Faith, Hope and Charity.  These are mentioned in the Bible in the First Epistle to the Corinthians chapter 13 verse 13.  These virtues are also very important in the Judaic and Muslim traditions.

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Ethics
Justice
Seven deadly sins

Ethics

Virtue


The International Union of Pure and Applied Chemistry (IUPAC) is an international organisation that represents chemists in individual countries. It governs everything to do with chemicals, elements and new discoveries. Every chemical known has a common name and a IUPAC name. This is also true for the Periodic Table of the Elements. Every element's name has been approved by IUPAC. This rule does not apply to those elements still given temporary names. The organisation was founded in 1919.

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Chemistry


Paris Opéra or the Opéra National de Paris is the most important opera company of France. It stages performances at the Opéra Bastille and Opéra Garnier in Paris. The theatre is also the home of the Paris Opéra Ballet.

Other opera houses in Paris are the Théâtre du Châtelet, Opéra-Comique and Théâtre des Champs-Élysées.

History
King Louis XIV allowed Jean-Baptiste Lully to start the Académie Royale de Musique in 1672. This was an organization that included opera, ballet, and music. The ballet company was part of the opera company. Then Louis XIV started the ballet school, called Académie Royale de Danse, in 1661. From 1671 until Lully's death in 1687, the school was directed by the great dancing master Pierre Beauchamp, the man who set down the five positions of the feet.

In 1713 King Louis XIV made the Opera company a state institution. There was a group of professional dancers called Le Ballet de l'Opéra. From that time until 1875 they used lots of theatres, each one of which was destroyed by a fire. All these companies were called Paris Opéra or Opéra de Paris.

On 29 October 1873, the old Paris Opéra, known as the Théâtre de l'Académie Royale de Musique, which had been used since 1821, was destroyed by a fire which burned for 27 hours. By 1875 the opera company moved to the new Palais Garnier which was part of the rebuilding of Paris by Emperor Napoleon III.

When the Opéra Bastille was built in 1989 the company chose it as their main theatre.

Other websites
 Official site

Theatres in Paris

Paris Opera