History of calendar

Throughout history, people have relied on calendars to keep track of activities.This means that people have been making and using ways to keep track of days and more significant parts of time for a very long time. Archaeologists have found ways to keep track of the time at least as old as the Neolithic. Most historical societies used natural time units like the day, the solar year, and the lunation to track how long things took. Calendars are a way to keep track of time in a specific way .The Egyptian and Sumerian calendars were also made at this time. More calendar systems from the Ancient Near East show up in the archaeological record during the Iron Age. They are primarily based on the Babylonian calendar, though. This is included in the Persian Empire's calendar, which led to the Zoroastrian and Hebrew calendars.

The Hellenistic period

In Classical Greece, a lot of different Hellenic calendars were made. In the Hellenistic period, these calendars spread outside of Greece's direct influence, giving rise to the Hindu calendars and the ancient Roman calendar. In ancient times, calendars were often lunisolar, which meant that they used interplanetary months to make the solar and lunar years match up. People's observations dominated in this scenario. The Coligny calendar, a fragmented 2nd-century calendar, may have been an example of an early attempt to represent the intercalation pattern algorithmic-ally. However, the Roman calendar still had traces of a pre-truscan solar year ten months long.

The Julian calendar

Julian Caesar made changes to the Roman calendar in 45 BCE, when the calendar was first changed in history.

Length of the year

In 1079, the length of the year was changed to 365.24219858156 days. The size of the year changes in the sixth decimal place during a person's lifetime; hence the above statement is pretty close to the fact. Compared to today, the year's duration at the end of the nineteenth century was 365.242196 days, whereas it is currently 365.242190 days. it was considered an improvement over the Julian calendar. It is now widely accepted as the main calendar for secular purposes worldwide.

A calendar is a long-term timekeeper.

It is a way to keep track of time over a long period. Convention says that a day is the smallest unit of time. Timekeeping is when you measure how many minutes, hours, or days are left in a day. This definition is so broad because there are so many different ways to make calendars. Because some calendars follow rules, some calendars are based on abstract, perpetually repeating cycles that have no connection to the astronomical world. Some calendars are based on astronomical observations, some are very detailed and redundant, and some have a lot of ambiguities and gaps. Some calendars are written down, and others are passed down through oral tradition.

The history of calendars, that is, of people creating and using methods for keeping track of days and larger divisions of time, covers a practice with very ancient roots.

Archeologists have reconstructed methods of timekeeping that go back to prehistoric periods at least as old as the Neolithic. The natural units for timekeeping used by most historical societies are the day, the solar year and the lunation. Calendars are explicit schemes used for timekeeping. The first recorded calendars date to the Bronze Age, dependent on the development of writing in the Ancient Near East, the Egyptian and Sumerian calendars.

A larger number of calendar systems of the Ancient Near East appear in the Iron Age archeological record, based on the Babylonian calendar. This includes the calendar of the Persian Empire, which in turn gave rise to the Zoroastrian calendar as well as the Hebrew calendar.

A great number of Hellenic calendars developed in Classical Greece, and in the Hellenistic period also influenced calendars outside the immediate sphere of Greek influence, giving rise to the various Hindu calendars as well as to the ancient Roman calendar.

Calendars in antiquity were usually lunisolar, depending on the introduction of intercalary months to align the solar and the lunar years. This was mostly based on observation, but there may have been early attempts to model the pattern of intercalation algorithmically, as evidenced in the fragmentary 2nd-century Coligny calendar. Nevertheless, the Roman calendar contained very ancient remnants of a pre-Etruscan 10-month solar year.

The Roman calendar was reformed by Julius Caesar in 45 BCE. The Julian calendar was no longer dependent on the observation of the new moon but simply followed an algorithm of introducing a leap day every four years. This created a dissociation of the calendar month from the lunation. In the 11th century in Persia, a calendar reform led by Khayyam was announced in 1079, where the length of the year was measured as 365.24219858156 days. Given that the length of the year is changing in the sixth decimal place over a person's lifetime, this is outstandingly accurate. For comparison the length of the year at the end of the 19th century was 365.242196 days, while today it is 365.242190 days.

The Gregorian calendar was introduced as a refinement of the Julian calendar in 1582, and is today in worldwide use as the de facto calendar for secular purposes.

A calendar is a system of organizing units of time for the purpose of reckoning time over extended periods. By convention, the day is the smallest calendrical unit of time; the measurement of fractions of a day is classified as timekeeping. The generality of this definition is due to the diversity of methods that have been used in creating calendars. Although some calendars replicate astronomical cycles according to fixed rules, others are based on abstract, perpetually repeating cycles of no astronomical significance. Some calendars are regulated by astronomical observations, some carefully and redundantly enumerate every unit, and some contain ambiguities and discontinuities. Some calendars are codified in written laws; others are transmitted by oral tradition.