Historic Calendars Timeline

Historic Calendars 28

3100 BC – 2686 BC The Egyptian calendar -- 365 days The ancient Egyptian calendar is the first solar calendar in history -- a 365-day year divided into 12 months of 30 days each plus five intercalary ("epagomenal") days. The year is divided into three seasons of four months each: Akhet (inundation, when the Nile floods), Peret (emergence, when the floodwaters recede and planting begins) and Shemu (harvest). The calendar year begins when Sirius (Sopdet) first appears on the horizon at dawn after 70 days of invisibility -- an event that approximately coincides with the beginning of the Nile flood. The Egyptian calendar is adopted by the Romans (as the Julian calendar, introduced by Julius Caesar on the advice of Alexandrian astronomers) and ultimately underpins the Gregorian calendar used worldwide today.
713 BC – 46 BC Roman Republican calendar 355 days and a floating leap month Tradition credits King Numa Pompilius with a 355-day Roman calendar of twelve months. Priests added a leap month at will, often for political reasons, and by the time of Julius Caesar the calendar had drifted about three months from the seasons.
499 BC Babylonians fix a 19-year leap-month cycle The Babylonian lunisolar calendar From around 499 BC the Babylonians add a thirteenth month seven times in every nineteen years, keeping their lunar months in step with the solar year. The same cycle still underlies the Hebrew calendar.
238 BC The Canopus Decree proposes a leap day Ptolemaic Egypt Under Ptolemy III, Egyptian priests decree an extra day every four years to stop the 365-day civil calendar drifting through the seasons. The reform is not kept, but Julius Caesar later adopts the idea.
104 BC Han China adopts the Taichu calendar Grand Inception calendar Emperor Wu of Han introduces the Taichu calendar, a lunisolar calendar that starts the year near the winter solstice and sets a pattern Chinese calendars follow for centuries.
45 BC – present Julian calendar 365 days with a leap day every four years Julius Caesar, advised by the astronomer Sosigenes, replaces the Roman calendar with a solar year of 365 days and a leap day every fourth year, starting on 1 January 45 BC. It stays the calendar of Europe for more than 1,600 years and is still used by several Orthodox churches.
36 BC The earliest Long Count date Chiapa de Corzo, Mexico A stela fragment carries the oldest known Long Count date in Mesoamerica, counting days from a mythical starting point in 3114 BC — a calendar that would run unbroken for over a thousand years.
359 – present Hebrew calendar Fixed by calculation Tradition holds that Hillel II published the rules for calculating the Hebrew calendar in 359, replacing month starts set by sighting the new moon. The lunisolar calendar counts years from the creation of the world and remains in use for Jewish religious life.
525 Dionysius Exiguus introduces Anno Domini dating Counting years from the birth of Christ While compiling Easter tables in Rome, the monk Dionysius Exiguus numbers years from the incarnation of Christ instead of from the reign of Diocletian. Bede later spreads the system, and it becomes the year count of the Western world.
638 – present Islamic calendar The Hijri calendar Around 638 Caliph Umar adopts a calendar that counts years from the Hijra, Muhammad's journey to Medina in 622. Its twelve lunar months give a year of 354 or 355 days, so its months move through the seasons.
909 The last Long Count date ever carved Toniná, Mexico Monument 101 at Toniná bears the final date recorded in the Long Count system. The calendar had run for nearly a thousand years of continuous history, and then stopped.
1079 Jalali calendar introduced in Persia Omar Khayyam The Seljuk sultan Malik-Shah introduces a solar calendar worked out by astronomers including Omar Khayyam. It starts the year at the spring equinox and is more accurate than the Gregorian calendar adopted in Europe five centuries later.
1280 Completion of the Shoushi calendar Astronomer Guo Shoujing finalizes a new calendar for the Yuan dynasty Chinese astronomer Guo Shoujing, working under a commission from Kublai Khan, completed the Shoushi calendar in 1280. It calculated the length of the tropical year to within about 26 seconds of the modern value, making it one of the most accurate calendars produced anywhere before the Gregorian reform. The calendar was formally adopted across the Yuan Empire the following year.
1428 – 1521 The Aztec calendar -- two interlocking wheels The Aztec calendar system, inherited from earlier Mesoamerican cultures (particularly the Maya and Zapotec), consists of two interlocking cycles: the xiuhpohualli (365-day solar year, 18 months of 20 days plus 5 dangerous "empty days") and the tonalpohualli (260-day ritual calendar, used for divination, naming ceremonies and scheduling religious events). The two calendars mesh like interlocking gears, completing a full cycle (the 52-year "Calendar Round" or xiuhmolpilli) every 52 years -- a period as significant to the Aztecs as a century is to us. At the end of each 52-year cycle, there is existential anxiety: the world might end if the gods are not appeased. The New Fire Ceremony (Toxiuhmolpilia) -- the extinguishing of all fires followed by drilling new fire on the chest of a sacrificial victim -- marks the beginning of each new 52-year cycle and the world's renewal.
1428 – 1521 The tonalpohualli -- the 260-day ritual calendar The tonalpohualli ("count of days," 260-day ritual calendar) is the most distinctive element of Mesoamerican calendrical science -- a divinatory calendar used for naming children, scheduling rituals, predicting the outcomes of undertakings and determining the destiny of individuals from birth. It consists of 20 day signs (each associated with a deity) combined with 13 numbers, cycling through 260 unique day combinations before repeating. The 260-day period corresponds to the human gestation period (approximately nine 29-day lunar months), the growing season in highland Mexico, and the period between the zenith passage of the sun at the latitude of central Mexico -- making it simultaneously practical, astronomical and symbolic. Each day combination has a specific set of associations (favourable, unfavourable, specific deities, specific activities) that the tonalpouhqui (day-sign reader, diviner) interprets for clients. The tonalpohualli governs the scheduling of every important activity in Aztec life from birth to death -- when to plant, when to travel, when to marry, when to go to war.
1582 Gregorian calendar introduced Pope Gregory XIII reforms the Julian calendar A papal bull by Pope Gregory XIII, Inter gravissimas, decreed that Thursday, 4 October 1582 would be followed by Friday, 15 October 1582, correcting centuries of drift in the Julian calendar. Catholic states including Spain, Portugal, the Italian states, and the Polish-Lithuanian Commonwealth adopted the new calendar immediately. Protestant and Orthodox countries kept the Julian calendar for generations afterward, splitting Europe into two dating systems for centuries.
1699 Peter the Great reforms the Russian calendar Decree moves the Russian New Year to 1 January and adopts Anno Domini dating Tsar Peter I decreed that Russia would begin counting years from the birth of Christ rather than from the Byzantine creation era, and that the new year would start on 1 January instead of 1 September. The reform took effect at the start of 1700 and was part of Peter's broader effort to align Russian customs with Western Europe. Russia retained the Julian calendar itself for another two centuries.
1752 Britain adopts the Gregorian calendar Eleven days are skipped to align with continental Europe Under the Calendar (New Style) Act 1750, Great Britain and its colonies switched from the Julian to the Gregorian calendar. Wednesday 2 September 1752 was followed directly by Thursday 14 September 1752, so the eleven intervening dates never occurred.
1793 French Republican Calendar adopted Revolution reorders time itself The National Convention formally adopted a new calendar dividing the year into twelve thirty-day months with new names, retroactively dated from the proclamation of the Republic in September 1792. The calendar remained in official use in France until 1805.
1806 France returns to the Gregorian calendar End of the Republican calendar Napoleon abolishes the French Republican calendar, with its ten-day weeks and months named after the weather, and France returns to the Gregorian calendar on 1 January 1806.
1872 Japan announces adoption of Gregorian calendar Meiji government decrees switch from lunisolar calendar The Meiji government issued a decree replacing Japan's traditional lunisolar calendar with the Gregorian calendar, effective January 1, 1873. The reform was part of a broader modernization of Japanese institutions along Western lines.
1912 Republic of China adopts the Gregorian calendar The first year of the Republic The new Republic of China adopts the Gregorian calendar from 1 January 1912, numbering years from the founding of the Republic. The traditional lunisolar calendar remains in use for festivals such as the Spring Festival.
1918 Soviet Russia switches to the Gregorian calendar 31 January is followed by 14 February The Bolshevik government drops the Julian calendar, so that 31 January 1918 is followed by 14 February. The October Revolution of 1917 is from then on commemorated in November.
1923 Greece adopts the Gregorian calendar The last in Europe Greece moves from the Julian to the Gregorian calendar, skipping from 15 February to 1 March 1923, the last European country to do so for civil use.
1925 Iran adopts the Solar Hijri calendar An official solar calendar Iran's parliament makes the Solar Hijri calendar, a descendant of the Jalali calendar, the official calendar of the country. Its year begins at the spring equinox with Nowruz.
1926 Turkey adopts the Gregorian calendar Atatürk's reforms As part of Mustafa Kemal Atatürk's modernising reforms, Turkey replaces the Islamic and Rumi calendars with the Gregorian calendar from 1 January 1926.
1929 – 1940 Soviet Union introduces the continuous working week The Soviet calendar To keep factories running every day, the Soviet Union introduces a five-day and later a six-day week, with workers given different rest days. The experiment is abandoned in 1940 and the seven-day week returns.
1957 India adopts the Saka national calendar The Indian national calendar India introduces a reformed Saka calendar as its official civil calendar alongside the Gregorian one, beginning on 22 March 1957.