# Anniversary

An anniversary is the date on which an event took place or an institution was founded.
Most countries celebrate national anniversaries, typically called national days. These could be the date of independence of the nation or the adoption of a new constitution or form of government. There is no definite method for determining the date of establishment of an institution, and it is generally decided within the institution by convention. The important dates in a sitting monarch's reign may also be commemorated, an event often referred to as a "jubilee".

## Names

* Birthdays are the most common type of anniversary, on which someone's birthdate is commemorated each year. The actual celebration is sometimes moved for practical reasons, as in the case of an official birthday or one falling on February 29.
* Wedding anniversaries are also often celebrated, on the same day of the year as the wedding occurred.
* Death anniversaries.
The Latin phrase dies natalis (literally "birth day") has become a common term, adopted in many languages, especially in intellectual and institutional circles, for the anniversary of the founding ("legal or statutory birth") of an institution, such as an alma mater (college or other school). In ancient Rome, the [dies] Aquilae natalis was the "birthday of the eagle", the anniversary of the official founding of a legion.
Anniversaries of nations are usually marked by the number of years elapsed, expressed with Latin words or Roman numerals.

### Numerical

Latin terms for anniversaries are mostly straightforward, particularly those relating to the first thirty years (1–30), or multiples of ten years (30, 40, 50, 60, 70 etc.), or multiples of centuries or millenniums (100, 200, 300, 1000, 2000, 3000, etc.). In these instances, the name of the anniversary is generally derived from the Latin word(s) for the respective number of years. When anniversaries relate to fractions of centuries (125, 150, 175, 225, 250, 275 years—i.e. 1.25, 1.5, 1.75, 2.25, 2.5, and 2.75 centuries), the situation is not as simple.
Roman fractions were based on a duodecimal system. From 1⁄12 to 8⁄12 they were expressed as multiples of twelfths (uncia "twelfth"; the source of the English words inch and ounce) and from 9⁄12 to 11⁄12 they were expressed as multiple twelfths less than the next whole unit—i.e. a whole unit less 3⁄12, 2⁄12 or 1⁄12 respectively. There were also special terms for quarter (quadrans), half (semis), and three-quarters (dodrans). Dodrans is a Latin contraction of de-quadrans which means "a whole unit less a quarter" (de means "from"; quadrans means "quarter"). Thus for the example of 175 years, the term is a quarter century less than the next whole (bi)century or 175 = (−25 + 200).
In Latin, it seems that this rule did not apply precisely for 1+1⁄2. While secundus is Latin for "second", and bis for "twice", these terms are not used such as in sesqui-secundus. Instead sesqui (or ses) is used by itself.
| Anniversary | Latin-derived term | Other terms | Comments |
| 6 months | Semiannual | | 'Biannual' means twice in a year, or a malapropism meaning once every two years ('biennial'). |
| 6 months | Biannual | | 'Biannual' means twice in a year, or a malapropism meaning once every two years ('biennial'). |
| 1 year | Annual | Paper | |
| 2 years | Biennial | Cotton | 'Biennial' means once every two years, or a malapropism meaning twice in a year ('biannual'). |
| 3 years | Triennial | Leather | |
| 4 years | Quadrennial | Linen | |
| 5 years | Quinquennial | Wood | |
| 6 years | Sexennial, Sextennial | Iron | Sexennial and sextennial are two different forms of the same word. |
| 7 years | Septennial | Wool | |
| 8 years | Octennial | Bronze | |
| 9 years | Novennial | Copper | |
| 10 years | Decennial | Tin Aluminum | |
| 10 years | Denary | Tin Aluminum | |
| 11 years | Undecennial | Steel | |
| 12 years | Duodecennial | Silk | |
| 121⁄2 years | | Parsley | A humorous or mock wedding anniversary celebrated in Northern Germany and the Netherlands, chosen because it is halfway to the silver anniversary. |
| 13 years | Tredecennial | Lace | |
| 14 years | Quattuordecennial | Ivory | |
| 15 years | Quindecennial | Crystal | |
| 16 years | Sexdecennial | Sapphire | Sapphire is separately used for other anniversaries |
| 17 years | Septdecennial | Orchid | |
| 18 years | Octdecennial | Quartz | |
| 19 years | Novdecennial | Jade | |
| 20 years | Vigintennial | China/Porcelain/emerald | |
| 20 years | Vicennial | China/Porcelain/emerald | |
| 20 years | Vicenary | China/Porcelain/emerald | |
| 20 years | Bidecennial | China/Porcelain/emerald | |
| 25 years | Quadranscentennial | Silver | |
| 30 years | Tricennial | Pearl | |
| 30 years | Tricenary | Pearl | |
| 35 years | Quintricennial | Coral | |
| 40 years | Quadragennial | Ruby | |
| 40 years | Quadragenary | Ruby | |
| 45 years | Quinquadragennial | Sapphire | |
| 50 years | Semicentennial | Golden | Previously, "jubilee" by itself was used to indicate celebrations at 50 year intervals |
| 50 years | Quinquagenary | Golden | Previously, "jubilee" by itself was used to indicate celebrations at 50 year intervals |
| 55 years | Quinquinquagennial | Emerald | |
| 55 years | Quinquinquagenary | Emerald | |
| 60 years | Sexagennial | Diamond | Diamond is separately used for the 75th anniversary, its use for 60th years being popularized by Diamond Jubilee of Queen Victoria |
| 60 years | Sexagenary | Diamond | Diamond is separately used for the 75th anniversary, its use for 60th years being popularized by Diamond Jubilee of Queen Victoria |
| 65 years | Quinsexagennial | Sapphire | Sapphire is separately used for other anniversaries |
| 70 years | Septuagennial | Platinum | |
| 70 years | Septuagenary | Platinum | |
| 75 years | Semisesquicentennial | Diamond | Diamond is separately used for the 60th anniversary. Semisesquicentennial can be broken down to understand its meaning: "semi" - half of + "sesqui" - in the ratio of 3:2 + "centennial" - 100 years. Broken out mathematically, 1/2 * 3/2 * 100 = 75. |
| 75 years | Demisesquicentennial | Diamond | Diamond is separately used for the 60th anniversary. Semisesquicentennial can be broken down to understand its meaning: "semi" - half of + "sesqui" - in the ratio of 3:2 + "centennial" - 100 years. Broken out mathematically, 1/2 * 3/2 * 100 = 75. |
| 80 years | Octogintennial | Oak | |
| 80 years | Octogenary | Oak | |
| 90 years | Nonagintennial | Granite | |
| 90 years | Nonagenary | Granite | |
| 100 years | Centennial | Obsidian | |
| 100 years | Centenary | Obsidian | |
| 125 years | Quasquicentennial | | Term is broken down as quasqui- (and a quarter) centennial (100 years). Quasqui is a contraction from quadrans "a quarter" plus the clitic conjunction -que "and". The term was coined by Funk and Wagnalls editor Robert L. Chapman in 1961. |
| 150 years | Sesquicentennial | | Term broken down as sesqui- (one and a half) centennial (100 years) |
| 175 years | Dodransbicentennial | | Dodrans is a Latin contraction of de-quadrans which means "a whole unit less a quarter" (de means "from"; quadrans means "quarter"). 175 years is a quarter century less than the next whole (bi)century (175 = 200 − 25). |
| 175 years | Dodrabicentennial | | Alternative Latin form of Dodransbicentennial |
| 175 years | Dequasbicentennial | | Alternative Latin form of Dodransbicentennial |
| 175 years | Dosquicentennial | | Dosquicentennial has been used in modern times and this is perhaps a modern contraction of "de-quadrans". |
| 175 years | Demisemiseptcentennial | | Probably a modern coined term: demisemiseptcentennial; literally one-half (demi-) × one-half (semi-) × seven (sept-) × 100 years (centennial)—also demisemiseptcentenary. |
| 175 years | Quartoseptcentennial | | Probably a modern coined term: quartoseptcentennial; literally one-quarter (quarto-) × seven (sept-) × 100 years (centennial)—also quartoseptcentenary. |
| 175 years | Terquasquicentennial | | A coined word for an anniversary of 175 years, but the elements of the word literally refer to an anniversary of 375 years, as follows: ter- (3) × quasqui- (11⁄4) × centennial (100 years) |
| 175 years | Septaquintaquinquecentennial | | Suggested by lexicographer Robert L. Chapman to William Safire; first appeared in Safire's column, "On Language" (The New York Times Magazine, February 12, 1995). It is a coined word for an anniversary of 175 years, but the elements of the word literally refer to an anniversary of 35,000 years, as follows: septaquinta- (70) × quinque- (5) × centennial (100 years) |
| 200 years | Bicentennial | | |
| 200 years | Bicentenary | | |
| 225 years | Quasquibicentennial | | |
| 250 years | Sestercentennial | | To express 2+1⁄2 in Latin it would be expressed as "half-three". The term relates to being halfway [from the second] to the third integer. In Latin this is "Sestertius", which is a contraction of semis (halfway) tertius (third)—hence Sestercentennial. |
| 250 years | Semiquincentennial | | Probably a modern coined term: semi- (half) × quin (5) × centennial (100 years) = 250 years. Used by Brown University in 2015. |
| 250 years | Bicenquinquagenary | | Used by Princeton University in 1996, Reading, Pennsylvania in 1998, and Washington and Lee University in 1999. It is a coined word for an anniversary of 250 years: bi- (2) × cen(t)- (100) + quinquagenary (50 years). |
| 250 years | Quarter-millennial | | |
| 275 years | Bicenterquasquigenary | |
| 300 years | Tercentennial | | |
| 300 years | Tercentenary | | |
| 300 years | Tricentennial | | |
| 300 years | Tricentenary | | |
| 350 years | Sesquarcentennial | | Sesquarcentennial is a modern coined term; sesquarcentennial for 350 years is deduced here from the "Sestertius" definition for 250 years above. For 350 years it relates to being halfway from the third to the fourth integer; thus a contraction of semis (halfway) and quartus (fourth); hence Sesquarcentennial. Semiseptcennial is probably a modern coined term: semi- (half) × sept (7) × cen(t)- (100) × centennial (350 years). |
| 350 years | Semiseptcentennial | | Sesquarcentennial is a modern coined term; sesquarcentennial for 350 years is deduced here from the "Sestertius" definition for 250 years above. For 350 years it relates to being halfway from the third to the fourth integer; thus a contraction of semis (halfway) and quartus (fourth); hence Sesquarcentennial. Semiseptcennial is probably a modern coined term: semi- (half) × sept (7) × cen(t)- (100) × centennial (350 years). |
| 375 years | Terquasquicentennial | |
| 400 years | Quadricentennial | | |
| 400 years | Quadricentenary | | |
| 400 years | Quatercentenary | | |
| 450 years | Sesquincentennial | | |
| 500 years | Quincentenary | | |
| 500 years | Quincentennial | | |
| 600 years | Sexacentennial | | |
| 600 years | Sexcentenary | | |
| 700 years | Septcentennial | | Probably a coined term; earliest known use in March 1988. Chiang Mai Septcentennial Stadium (Chiang Mai, Thailand) was completed in 1991. |
| 700 years | Septuacentennial | | Probably a coined term; earliest known use in March 1988. Chiang Mai Septcentennial Stadium (Chiang Mai, Thailand) was completed in 1991. |
| 800 years | Octocentennial | | |
| 800 years | Octocentenary | | |
| 900 years | Nonacentennial | | |
| 1000 years | Millennial | | |
| 1500 years | Sesquimillennial | | Term broken down as sesqui- (one and a half) millennial (1000 years) |
| 2000 years | Bimillennial | | |
| 3000 years | Trimillennial | | |
| 4000 years | Quadrimillennial | | |
| 5000 years | Quinmillennial | | |
| 6000 years | Sexmillennial | | |
| 7000 years | Septmillennial | | |
| 8000 years | Octomillennial | | |
| 9000 years | Novamillennial | | |
| 10,000 years | Decamillennial | | |
| 100,000 years | Centamillennial | | |

## Symbols

Many anniversaries have special names. Etiquette in Society, in Business, in Politics and at Home by Emily Post, published in 1922, contained suggestions for wedding anniversary gifts for 1, 5, 10, 15, 20, 25, 50, and 75 years. Wedding anniversary gift suggestions for other years were added in later editions and publications; they now comprise what is referred to as the "traditional" list. Generally speaking, the longer the period, the more precious or durable the material associated with it.
There are variations according to some national traditions. There exist numerous partially overlapping, partially contradictory lists of anniversary gifts (such as wedding stones), separate from the "traditional" names. The concepts of a person's birthday stone and zodiac stone, by contrast, are fixed for life according to the day of the week, month, or astrological sign corresponding to the recipient's birthday.