| December 30 | Index | January 1 |
| Every Year |
December 31 is the 365th day of the year (366th in leap years) in the Gregorian calendar. |
| Every Year |
When epochs refer to January 0, it is an alternate name for December 31 of the previous year.
January 0 is used to keep the epoch in the same year instead of referring to a previous year. |
| December 30 | Index | January 1 |