The Gregorian calendar, and how it differs from the Julian
The Gregorian calendar is the calendar most of the world uses today. Pope Gregory XIII introduced it in 1582 to fix the older Julian calendar, which had drifted 10 days away from the seasons. The two calendars are now 13 days apart.
The leap year rule
| Julian calendar | Gregorian calendar | |
|---|---|---|
| Introduced | 45 BC, by Julius Caesar | 1582, by Pope Gregory XIII |
| Leap years | Every 4th year | Every 4th year, except century years not divisible by 400 |
| Average year | 365.25 days | 365.2425 days |
| Drift from the seasons | 1 day every 128 years | 1 day every ~3,200 years |
See the rule in action with the leap year checker: 2000 was a leap year, but 1900 and 2100 are not.
How far apart are the calendars?
| Period (Gregorian dates) | Gregorian is ahead by |
|---|---|
| Oct 15, 1582 – Feb 28, 1700 | 10 days |
| Mar 1, 1700 – Feb 28, 1800 | 11 days |
| Mar 1, 1800 – Feb 28, 1900 | 12 days |
| Mar 1, 1900 – Feb 28, 2100 | 13 days |
| From Mar 1, 2100 | 14 days |
When countries switched
| Country or region | Switched | Notes |
|---|---|---|
| Italy, Spain, Portugal, Poland | October 1582 | Thursday, October 4 was followed by Friday, October 15 |
| France | December 1582 | December 9 was followed by December 20 |
| Catholic German states, Netherlands (south) | 1583–1584 | |
| Protestant German states, Denmark, Norway | 1700 | |
| Great Britain, Ireland and the American colonies | September 1752 | Wednesday, September 2 was followed by Thursday, September 14 |
| Sweden and Finland | 1753 | |
| Japan | 1873 | replaced the lunisolar calendar |
| China | 1912 (officially 1929) | |
| Russia | February 1918 | January 31 was followed by February 14 |
| Greece | 1923 | the last country in Europe to switch for civil use |
| Turkey | 1926 |
Because Britain and its colonies switched in 1752, George Washington was born on February 11, 1731, in the old style, but we celebrate February 22, his birthday in the new style. The full story is in our history of timekeeping, Keeping Time.
Questions people ask
What is the difference between the Julian and Gregorian calendars?
Both have 365 days with a leap day every four years, but the Gregorian calendar skips the leap day in century years not divisible by 400 (1700, 1800, 1900, 2100). That makes its average year 365.2425 days, much closer to the solar year than the Julian 365.25.
How many days apart are the two calendars?
13 days since March 1, 1900, and until February 28, 2100, when the gap grows to 14. For example, January 1 in the Julian calendar is January 14 in the Gregorian.
Who still uses the Julian calendar?
Several Orthodox churches, including the Russian, Serbian and Georgian churches, use it to set religious holidays. That's why their Christmas falls on January 7.
Is the Julian date the same as the Julian calendar?
No. A Julian date is a day count, either the day of the year (26292) or the astronomers' Julian Day Number. It has nothing to do with which calendar you use.
Related: Julian date today · calendar with week numbers · leap year checker