Editing Year (section)

=== Julian calendar ===
In the [[Julian calendar]], the average (mean) length of a year is 365.25 days. In a non-leap year, there are 365 days, in a leap year there are 366 days. A leap year occurs every fourth year during which a leap day is [[intercalation (timekeeping)#Solar calendars|intercalated]] into the month of February. The name "Leap Day" is applied to the added day.

In astronomy, the [[Julian year (astronomy)|Julian year]] is a unit of time defined as 365.25 days, each of exactly {{val|86400}} [[second]]s ([[SI base unit]]), totaling exactly 31,557,600 seconds in the Julian astronomical year.<ref>{{cite web |publisher= International Astronomical Union IAU |url=http://www.iau.org/science/publications/proceedings_rules/units/ |title=SI units |access-date=February 18, 2010}}</ref><ref>{{cite journal |first=George A. |last=Wilkins |url= http://www.iau.org/static/publications/stylemanual1989.pdf |title=The IAU Style Manual |year= 1989 |journal= IAU Transactions |volume= XXB}}</ref>

==== Revised Julian calendar ====
The [[Revised Julian calendar]], proposed in 1923 and used in some [[Eastern Orthodox Church]]es, has 218 leap years every 900 years, for the average (mean) year length of {{val|365.2422222}} days, close to the length of the mean tropical year, {{val|365.24219}} days (relative error of 9·10). In the year 2800 CE, the Gregorian and Revised Julian calendars will begin to differ by one calendar day.<ref>{{Cite journal |bibcode = 1924PA.....32..407S|title = The new calendar of the eastern churches|last1 = Shields |first1 = Miriam Nancy|journal = Popular Astronomy|year = 1924|volume = 32|pages = 407}}</ref>