GitHub repository: siddhikasriram/Julian-date
Primary language: Jupyter Notebook
Created: 2021-06-22T17:47:47Z
Description: Julian days are primarily used by astronomers to calculate the time elapsed since between two events. The purpose of the Julian date is to make it easy for computing the difference between one calendar date and another calendar date. The Julian calendar is important to historians because it was used worldwide for over 16 centuries, and in various parts of the world for another three centuries after that. Julian day is the continuous count of the days right from the beginning of the Julian period, which is January 1st of 4713 BC, 12 noon. The astronomical day had begun at noon ever since Ptolemy chose to begin the days for his astronomical observations at noon. He chose noon because the transit of the Sun across the observer's meridian occurs at the same apparent time every day of the year, unlike sunrise or sunset, which vary by several hours. The starting point for the Julian Calendar is the reference epoch. And since the origin of this calendar era is so long ago, Julian day can be quite large. In the upcoming years, other astronomers started adding fractions of the day to create Julian dates. Julian dates are usually represented as the Julian day number along with a decimal fraction added. The fraction of the day is found by converting the number of hours, minutes, and seconds after noon into the equivalent decimal fraction. A Julian calendar typically has two types of years: normal year (365.25 days) and leap year (366 days). The Julian calendar is slightly longer than the solar calendar. Julian's value is more than the solar value of 365.24 days. Therefore, the Julian calendar gains a day every 128 days. So, any event in the years 1901 - 2099 will have it’s date 13 days behind that of the Gregorian date. Terrestrial Time (TT) is an astronomical standard defined by the International Astronomical Union for time measurements of astronomical observations made from the Earth and Julian date is expressed in terms of TT.