- -8239
| Jun 05 | -BC- Presumed origin of Mayan Era of Creation. | Ref: 5 |
- -5777
| Jan 01 | -BC- Origin of Solar Cycle | Ref: 5 |
- -5502
| Aug 29 | -BC- Origin of Alexandrian Era | Ref: 5 |
- -4714
| Jan 01 | -BC- Origin of Julian Period (Year 0). | Ref: 4 |
- -4713
| Jan 01 | -BC- Julian Year 1 begins, at Greenwich mean noon. | Ref: 5 |
- -3963
| Oct 24 | -BC- Origin of Hevelius' Mundane Era. | Ref: 5 |
- -3114
| Sep 07 | -BC- Presumed origin of Mayan "long count" calendar system | Ref: 5 |
- -3102
| Feb 18 | -BC- Origin of Kali Era (India). | Ref: 5 |
- -2781
| Jul 19 | -BC- Presumed start of Egyptian calendar | Ref: 5 |
- -747
| Feb 26 | -BC- Origin of Era of Nabonassar. | Ref: 5 |
- -432
| Jul 13 | -BC- Origin of Metonic Cycle. | Ref: 5 |
- -309
| Apr 03 | -BC- Origin of Seleucid Era. | Ref: 5 |
- -245
| Apr 03 | -BC- Origin of Era of Arsaces. | Ref: 5 |
- -125
| Oct 19 | -BC- Origin of Era of Tyre. | Ref: 5 |
- -57
| Feb 22 | -BC- Origin of Vikrama Samvat Era (India). | Ref: 5 |
- -45
| Jan 01 | -BC- Origin of Julian Era; Julian calendar begins. | Ref: 74 |
| Feb 29 | -BC- The first Leap Day is recognized by proclamation of Julius Caesar. Under the old Roman calendar the last day of February was the last day of the year. | Ref: 2 |
- -38
| Jan 01 | -BC- Origin of Era of Spain (Cesars). | Ref: 5 |
- -36
| Dec 09 | -BC- The earliest date found (as of 1989) in the New World. It was reconstructed from a Mayan stone fragment found in Chiapa de Corzo in Mexico. | Ref: 5 |
- -30
| Jan 01 | -BC- Origin of Actian Era. | Ref: 5 |
- -26
| Aug 27 | -BC- Origin of Egyptian Era. | Ref: 5 |
- -1
| Jan 01 | -BC- Origin of Era of Pisa. | Ref: 5 |
| Mar 01 | -BC- Start of revised Julian calendar in Rome. | Ref: 5 |
- 1
| Jan 01 | Origin of Christian Era. | Ref: 5 |
| Mar 25 | Roman Church historian Dionysius Exiguus (ca.500-550), in calculating his history of the Christian Church, took this day as the supposed date of the Annunciation. March 25th afterward became the first day of the calendar year, until the Gregorian Calendar Reform of 1753 changed the day to January first. | Ref: 5 |
- 78
| Mar 03 | Origin of Saka Era (India). | Ref: 5 |
- 284
| Aug 29 | Origin of Era of Diocletian (Martyrs). | Ref: 5 |
-
- 463
| Jul 16 | Start of Lunar Cycle of Hilarius. | Ref: 5 |
- 597
| Dec 25 | England adopts Julian calendar. | Ref: 5 |
- 632
| Jun 16 | Origin of Persian [Yezdegird] Era. | Ref: 5 |
- 638
| Jan 23 | Start of Islamic calendar. | Ref: 5 |
- 990
| Jan 01 | Russia adopts Julian calendar. | Ref: 5 |
- 1079
| Mar 16 | Iran adopts solar Hijrah calendar. | Ref: 5 |
- 1556
| Mar 28 | Origin of Fasli Era (India). | Ref: 5 |
- 1581
| Mar 25 | Last New Year's Day in European Catholic countries; Gregorian calendar moves it to Jan 1, 1582. | Ref: 10 |
- 1582
| Jan 01 | Gregorian calendar now in effect and today is New Year's Day in Holland, Flanders, France, Italy, Portugal & Spain. | Ref: 10 |
| Oct 15 | The first day of the Gregorian calendar by the order of Pope Gregory XIII. The previous day was October 4th on the Julian calendar. Britain will adopt the Gregorian calendar on September 2nd, 1752; the Soviet Union will adopt the Julian calendar on January 31st, 1918. | Ref: 5 |
| Dec 10 | France begins use of Gregorian calendar. | Ref: 5 |
| Dec 14 | Zealand/Brabant Netherlands adopt Gregorian calendar, tomorrow is 12/25. | Ref: 5 |
| Dec 15 | Spanish Netherlands/Denmark/Norway adopt Gregorian calendar. | Ref: 5 |
| Dec 20 | The Gregorian Calendar is introduced in France. | Ref: 62 |
| Dec 21 | Flanders adopts Gregorian calendar, tomorrow is Jan 1 1583. | Ref: 5 |
| Dec 25 | Zealand/Brabant adopts Gregorian calendar, yesterday was Dec 14th. | Ref: 5 |
- 1583
| Jan 12 | Holland begins use of Gregorian calendar (yesterday was 1/1/1583). | Ref: 5 |
| Feb 21 | Groningen Netherlands begins using Gregorian calendar. | Ref: 5 |
- 1584
| Jan 07 | Last day of the Julian calendar in Bohemia & Holy Roman empire. | Ref: 5 |
| Jan 17 | Bohemia adopts the Gregorian calendar. | Ref: 5 |
| Jan 22 | Parts of Switzerland adopt Gregorian calendar (& parts in 1812). | Ref: 5 |
- 1612
| Feb 06 | Christopher Clavius calendar reformer, dies (birth date unknown). | Ref: 5 |
- 1622
| Jan 01 | Papal Chancery adopts Jan 1 as beginning of the year (was Mar 25). | Ref: 5 |
- 1694
| Sep 22 | Lord Chesterfield letter writer; introduced Gregorian calendar (1752), is born. | Ref: 5 |
- 1699
| Dec 20 | Peter the Great orders Russian New Year changed-Sept 1 to Jan 1. | Ref: 5 |
- 1700
| Jan 01 | Protestant West-Europe (except England) begin using Gregorian calendar. | Ref: 5 |
| Jan 01 | Russia replaces Byzantines with Julian calendar. | Ref: 5 |
| Feb 19 | Last day of the Julian calendar in Denmark. | Ref: 5 |
| Dec 31 | Frisia/Groningen adopt Gregorian calendar, tomorrow is 1/12/1701. | Ref: 5 |
- 1701
| Jan 12 | Parts of the Netherlands (Frisia & Groningen) adopt the Gregorian calendar (others 1 year later). | Ref: 5 |
| Apr 29 | Drenthe Netherlands adopts Gregorian calendar, tomorrow is May 12, 1701. | Ref: 5 |
| May 12 | Drenthe adopts Gregorian calendar (yesterday was 4/29/1701). | Ref: 5 |
- 1751
| Mar 25 | Last New Year's Day in England; British finally accept Gregorian calendar; New Year starts Jan 1. | Ref: 10 |
- 1752
| Jan 01 | Today is finally New Year's Day in England almost 170 years after France, Italy, etc. | Ref: 10 |
| Sep 02 | Britain and its colonies abandon the Julian calendar. The next day is September 14th on the Gregorian calendar. | Ref: 5 |
| Sep 03 | This day never happened nor the next 10 as England adopts Gregorian Calendar. People riot thinking the govt stole 11 days of their lives. | Ref: 5 |
| Sep 14 | Gregorian calendar finally adopted in Britain-170 years after rest of Europe. (Sept. 3-13 omitted) | Ref: 5 |
- 1793
| Oct 05 | The Revolutionary Calendar is adopted in France. This day becomes 14 Vendemiaire (grape harvest) Year II. Months were named for seasonal characteristics and years from the beginning of the revolution. | Ref: 62 |
| Nov 26 | Republican calendar replaces Gregorian calendar in France. | Ref: 5 |
- 1805
| Dec 31 | End of French Republican calendar; France returns to Gregorianism. | Ref: 5 |
- 1858
| Nov 17 | Origin of Modified Julian Period. | Ref: 5 |
- 1867
| Oct 16 | Alaska adopts the Gregorian calendar, crosses intl date line. | Ref: 5 |
- 1873
| Jan 01 | Japan adopts the Gregorian calendar; Origin of Japanese Era. | Ref: 17 |
- 1876
-
- 1893
| Jan 01 | Japan adopts the Gregorian calendar. | Ref: 5 |
- 1894
| Jan 01 | Denmark adopts Mid-European time. | Ref: 5 |
| Jun 28 | By an act of Congress, Labor Day became a federal holiday in the US The first Monday of September is when Labor Day is celebrated as a salute to working men and women across the country. | Ref: 4 |
- 1895
| Jan 01 | Norway adopts Mid-European time. | Ref: 5 |
- 1901
| May 30 | Memorial Day first observed in US. | Ref: 5 |
- 1912
| Feb 12 | China adopts the Gregorian calendar. | Ref: 5 |
- 1918
| Jan 01 | Last day of the Julian calendar in Finland. | Ref: 5 |
| Jan 14 | Finland & USSR adopts New Style (Gregorian) calendar. | Ref: 5 |
| Jan 31 | The Soviets abandon the Julian calendar. The following day was Februray 14th on the Gregorian calendar. | Ref: 17 |
| Feb 01 | Russia adopts Gregorian calendar (becomes Feb 14). | Ref: 5 |
| Feb 14 | The Soviets adopt the 400-year old Gregorian calendar. The previous day was January 31st. | Ref: 5 |
| Feb 15 | Estonia, Latvia & Lithuania adopt the Gregorian calendar. | Ref: 5 |
- 1920
| Mar 04 | Last day of Julian civil calendar in Greece. | Ref: 5 |
| Mar 18 | Greece adopts the Gregorian calendar. | Ref: 5 |
| Sep 04 | Last day of Julian civil calendar (in parts of Bulgaria). | Ref: 5 |
- 1921
| Nov 05 | Pres. Warren Harding proclaims Armistice Day to be a legal holiday on Nov. 11 commemorating WWI. | Ref: 10 |
- 1922
| Jan 30 | World Law Day, first celebrated. | Ref: 5 |
- 1923
| Oct 06 | USSR adopts experimental calendar. | Ref: 5 |
- 1925
| Mar 21 | Iran adopts Khorshidi solar Hijrah calendar. | Ref: 5 |
| Dec 26 | Turkey adopts Gregorian calendar. | Ref: 5 |
- 1931
| Oct 12 | First International Conference on Calendar Reform. | Ref: 5 |
- 1940
| Jun 26 | End of USSR experimental calendar; Gregorian readopted 6/27. | Ref: 5 |
| Jun 27 | USSR returns to the Gregorian calendar. | Ref: 5 |
- 1946
-
- 1955
| Jan 25 | Columbia University scientists develop an atomic clock that is accurate to within one second in 300 years. | Ref: 2 |
- 1957
| Jan 01 | International Geophysical Year begins; ends 6/30/1958 (18-month year). | Ref: 5 |
| Mar 22 | Republic of India adopts Saka calendar along with Gregorian. | Ref: 5 |
| Jul 01 | The beginning of the first international geophysical year | Ref: 62 |
- 1958
| Dec 31 | International Geophyscial Year ends. | Ref: 5 |
- 1959
| Jul 01 | World Refugee Year begins. | Ref: 5 |
- 1965
| Jan 01 | International Cooperation Year begins. | Ref: 5 |
- 1968
| Feb 18 | British adopt year-round daylight savings time. | Ref: 5 |
- 1970
| Jan 01 | Revised calendar for Western (RC) Church goes into effect. | Ref: 5 |
- 1972
| Jan 01 | International Book Year begins. | Ref: 5 |
| Jun 30 | First leap second day; also 1981, 1982, 1983, 1985. | Ref: 5 |
| Dec 31 | Leap second day; also in 1973-79, 1987, 1998. | Ref: 5 |
- 1973
| Jan 16 | This is National Nothing Day, set aside each year for people to sit around for the entire day and just hang out. No celebrating, observing or honoring anything. Don’t even pick up the mail -- it’s only holiday bills, anyway. So, please, sit there with your hands folded and no talking. | Ref: 4 |
- 1974
| Jan 01 | World Population Year begins. | Ref: 5 |
- 1975
| Jan 01 | International Women's Year begins. | Ref: 5 |
- 1979
| Jan 01 | International Year of the Child begins. | Ref: 5 |
- 1980
| Jan 01 | International Decade of Water & Sanitation begins. | Ref: 5 |
- 1981
| Jan 01 | International Year for the Disabled begins. | Ref: 5 |
- 1983
| Jan 01 | World Communications Year begins. | Ref: 5 |
| Apr 17 | First National Coin Week begins. | Ref: 5 |
| May 25 | First National Missing Children's Day is proclaimed. | Ref: 5 |
- 1985
| Jan 01 | International Youth Year begins. | Ref: 5 |
| Jun 30 | For the 13th time since 1972, the world’s official timekeeper atomic clock ticked off one extra second at 23:59 Greenwich Mean Time (also called UCT, Universal Coordinated Time) or 7:59:59 p.m. in New York. The leap second was added to compensate for the gradual slowing of the Earth’s rotation. | Ref: 4 |
- 1986
| Jan 01 | International Peace Year begins. | Ref: 5 |
| Mar 11 | 1 million days since traditional foundation of Rome, 4/21/753 BC. | Ref: 5 |
- 1987
| Jan 01 | International Year of Shelter for Homeless begins. | Ref: 5 |
| Jan 01 | Year of the Reader begins. | Ref: 5 |
- 1989
| Jan 01 | Year of the Young Reader begins. | Ref: 5 |
- 1990
| Jul 08 | 12:34:56 on 7/8/90 (1234567890). | Ref: 5 |
- 1992
| Jan 01 | International Space Year begins. | Ref: 5 |
- 1994
| Jan 01 | International Year of Family. | Ref: 5 |
- 1995
| Jan 01 | International Year of Tolerance. | Ref: 5 |
- 1998
| Dec 01 | Cuba's Communist Party recommended that December 25th be re-established as a permanent holiday. (XDG, p 4A, 12/01/2003) | Ref: 83 |
- 1999
| Jan 01 | International Year of Elderly. | Ref: 5 |
- 3268
| Jan 23 | Beginning of 2nd Julian Period. | Ref: 5 |
|
Calendar Changes Chronology