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History of Calendars Timeline
(c. 3000 BCE – Present)The history of calendars traces humanity's efforts to organize time based on astronomical cycles. Ancient civilizations developed lunar, solar, and lunisolar calendars to track seasons, religious festivals, and agricultural activities. Key milestones include the Egyptian solar calendar, the Babylonian lunisolar system, the Roman Julian calendar introduced by Julius Caesar in 45 BCE, and the Gregorian calendar reform of 1582 under Pope Gregory XIII, which remains the internationally accepted civil calendar today. More Less
Ancient Calendars
Sumerian calendar established
2100 BC
The ancient Sumerian calendar, roughly dated to 2100 BC, divided a year into 12 lunar months of 29 or 30 days. They evolved over the centuries, but month names changed little until now.
Image source: Babylonian calendar
First Olympiad begins Greek timekeeping
Jul 1, 776 BC
The table of Greek Olympiads, following the four-year cycles between the Olympic Games from 1 July 776 BC, continued until the end of the 4th century AD.
Image source: Olympiad
Yaska quotes Jyotisha among Vedangas
500 BC
This study was one of the six ancient Vedangas, or ancillary science connected with the Vedas – the scriptures of Hinduism, which was quoted by 5th-century BC scholar Yaska.
Image source: Hindu astrology
Greek conciliar and festival calendars diverge
400 BC
Even more confusing, while the conciliar and festival years were about the same length in the 4th century BC, such was not regularly the case earlier or later.
Hindu calendars standardized via Indo-Greek transmission
200 BC - 1 BC
Most of the regional Hindu calendars are inherited from a system standardized in classical Hindu astronomy as adopted via Indo-Greek transmission in the final centuries BC, and reformed by Gupta era astronomers such as Aryabhata and Varāhamihira.
Image source: Hindu calendar
Varro introduces Ab urbe condita epoch
100 BC
In the first century BC, Marcus Terentius Varro introduced the Ab urbe condita epoch, assuming a foundation of Rome in 753 BC.
Image source: Ab urbe condita
Coligny calendar created
100 - 199
Early attempts to model the pattern of intercalation algorithmically are evidenced in the fragmentary 2nd-century Coligny calendar.
Image source: Coligny calendar
Brahma-siddhanta composed
500
The Jyotisha text Brahma-siddhanta, probably composed in the 5th century AD, discusses how to use the movement of planets, sun and moon to keep time and calendar.
Image source: Brahmagupta
Discovery of Warren Field calendar evidence
2013
In 2013, archaeologists unearthed ancient evidence of a 10,000-year-old calendar system in Warren Field, Aberdeenshire.
Image source: Warren Field
Religious Calendars
Oldest Roman calendar of saints compiled
350
The oldest calendar of saints of the Church of Rome was compiled in the mid-4th century, under Pope Julius I or Pope Liberius.
Key Facts
- Ancient Egyptians created one of the earliest solar calendars around 3000 BCE, dividing the year into 12 months of 30 days plus 5 extra days.
- The Babylonians developed a lunisolar calendar that influenced later Hebrew and Greek timekeeping systems.
- Julius Caesar introduced the Julian calendar in 45 BCE, establishing a 365-day year with a leap day every four years.
- The Gregorian calendar was introduced by Pope Gregory XIII in 1582 to correct the Julian calendar's drift, skipping 10 days that October.
- The Gregorian calendar was gradually adopted worldwide over centuries, with countries like Britain (1752) and Russia (1918) converting much later.
Source
This History of Calendars timeline was generated with the help of AI, using information found on the internet.
We work hard to keep these timelines accurate, but mistakes do get through. If you spot one, email us at [email protected] and we'll fix it for future visitors.
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