Pope Gregory XIII issued the papal bull Inter gravissimas in February 1582. Catholic countries adopted it immediately in October 1582: Italy, Spain, Portugal, Poland, France (December 1582). The calendar jumped 10 days forward (October 4 → October 15 in Rome).
The 1582 Reform: Catholic Countries First
Adoption Timeline by Country
The table below shows when major countries and regions switched to the Gregorian calendar, how many days were skipped, and any notable details:
| Country / Region | Year Adopted | Days Skipped | Notes |
|---|---|---|---|
| Italy, Spain, Portugal | 1582 | 10 days | First adopters — Oct 4 → Oct 15 |
| France | 1582 | 10 days | Dec 9 → Dec 20 |
| Poland | 1582 | 10 days | |
| Catholic German states | 1583–1584 | 10 days | |
| Protestant German states | 1700 | 11 days | |
| Denmark, Norway | 1700 | 11 days | Feb 18 → Mar 1 |
| Great Britain & colonies | 1752 | 11 days | Sep 2 → Sep 14 (includes American colonies) |
| Sweden | 1753 | 11 days | After a failed gradual transition starting 1700 |
| Japan | 1873 | — | Meiji government decree |
| Egypt | 1875 | — | |
| China (Republic) | 1912 | — | Widely used from 1929 |
| Bulgaria | 1916 | 13 days | |
| Russia | 1918 | 13 days | Jan 31 → Feb 14 (Old Style / New Style dates) |
| Romania, Yugoslavia | 1919 | 13 days | |
| Greece | 1923 | 13 days | Feb 15 → Mar 1 |
| Turkey | 1926 | — | |
| Saudi Arabia | 2016 | — | For government/civil use; Islamic calendar still official |
Why Did Britain 'Lose' 11 Days in 1752?
When Britain adopted the Gregorian calendar in September 1752, the calendar jumped from September 2 directly to September 14. This caused the popular legend that people rioted demanding their "11 days back," though historians debate whether riots actually occurred. The change was mandated by the Calendar (New Style) Act 1750.
Why Did Russia Adopt It So Late?
The Russian Orthodox Church used the Julian calendar and resisted the papal reform. After the Bolshevik Revolution, the Soviet government switched in 1918 — which is why the "October Revolution" actually happened in November by the Gregorian calendar.
FAQ
What calendar did the world use before Gregorian?
The Julian calendar, introduced by Julius Caesar in 46 BC. It had a small error (11 minutes too long per year) that accumulated to 10–13 days by the 16th–20th centuries.
Is the Gregorian calendar used everywhere today?
It is the international civil standard used by nearly all countries. Some countries also use other calendars — Saudi Arabia uses the Islamic calendar officially, Israel uses the Hebrew calendar for religious purposes, Japan uses the imperial calendar for official documents.
What is the difference between Old Style and New Style dates?
'Old Style' refers to Julian calendar dates, 'New Style' to Gregorian. This matters most for Russian, British, and Eastern European historical events before those countries adopted the Gregorian calendar.
When did the USA adopt the Gregorian calendar?
The American colonies were under British rule and adopted the Gregorian calendar along with Great Britain in 1752.