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Comparing calendars
Julian vs Gregorian
The Gregorian calendar is a small correction to the Julian: it drops three leap days every four centuries to track the solar year more closely. Sixteen centuries on, the two have drifted about thirteen days apart — which is why the Orthodox church still keeps Christmas in January.
| Attribute | Julian | Gregorian |
|---|---|---|
| Type | Solar | Solar |
| Origin | Introduced by Julius Caesar in 46 BCE | A 1582 reform of the Julian calendar, under Pope Gregory XIII |
| Year | 365 days, or 366 in a leap year (365.25 on average) | 365 days, or 366 in a leap year (365.2425 on average) |
| Months | 12, of 28–31 days | 12, of 28–31 days |
| Week | 7 days | 7 days |
| Leap rule | One leap day every 4 years, with no exception | One leap day every 4 years — but not in a century year unless it divides by 400 |
| Counts years from | The traditional birth of Christ (AD) | The traditional birth of Christ (AD / CE) |
| Where it’s used | Now about 13 days behind; kept by parts of the Orthodox church | The world’s common civil calendar |
See this moment on each: Julian calendar · Gregorian calendar. Or convert a specific date into both.