History of calender
From years we humans are using calendars to determine the date or days. In fact our very first task after getting up from sleep is to look at calendar and plan accordingly. But you ever thought that from where these calendars are originated ??
Let us start with What is calendar??
A calendar is a system of organizing days for social, religious, commercial or administrative purpose.This is done by giving names to periods of time typically like day, weeks, months and years.
The term calendar is taken from calendae, the term for first day of month in the roman calendar,related to the verb calare "to call out", referring to the "calling" of the new moon when it was first seen. Latin calendarium meant "account book, register" (as accounts were settled and debts were collected on the calends of each month). The Latin term was adopted in Old French as calendier and from there in Middle English as calender by the 13th century (the spelling calendar is early modern).
At different places on different times calendars were originated. The first historically attested and formulised calendars date to the Bronze Age, the Sumerian being the earliest, followed by Egyptian, Assyrian and Elamite calendars.A larger number of calendar systems of the Ancient Near East appear in the Iron Age archaeological record, based on the Assyrian and 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.
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.
There are 4 types of calendars in use currently:
- Gregorian calendar
- Religious calendar
- National calendar
- Fiscal calendar
Calendar system
A full calendar system has different dates for each different day, means they don't have weeks or months.The simplest calendar system just counts time periods from a reference date.There are different calendars based on their cycles like one level of cycles (with weeks and weekdays ) and two levels of cycles (with date, month, year).Currently we are using calendar with two cycles.
Now the question arises that how we can match these calendars.This can be done by with periodic phenomena:-
- Lunar calendars are synchronized to the motion of the Moon. Like the Islamic calendar.
- Solar calendars are based on perceived seasonal changes synchronized to the apparent motion of the Sun.Like the Persian calendar.
- Lunisolar calendars are based on a combination of both solar and lunar reckonings.Like the traditional calendar of China, the Hindu calendar in India, and the Hebrew calendar.
- The week cycle is an example of one that is not synchronized to any external phenomenon (although it may have been derived from lunar phases, beginning a new every month)
Now let us come to interesting questions...
Why do we have leap year ??Leap year refers t year with 366 days which comes every 4th year.This happens because our earth takes approx 365.25 days to revolve around the sun, so we consider 365 days as 1 yea and after 4 years we give it a value of 366 days. Simply 0.25*4=1 , 365+1=366.
Why do February has 28 days ??
Actually,no one knows why February was left with 28 and remained an unlucky month. It may be related to the fact that Romans honored the dead and performed rites of purification in February.But i will try to write one blog on February's 25 days after finding its answer.
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