The calendar used for international trade by several countries is the Gregorian calendar. Gregorian calendar was proclaimed by Pope Gregory XIII and most catholic states adopted this in the year 1582. Before Gregorian calendar came into existence, Julian calendar was used. In 1582, October 4th of Julian calendar was followed by October 15 of new Gregorian calendar to correct the differences between Julian and Gregorian calendars. In the Julian calendar every fourth year is a leap year and February consists of 29 days. In The Gregorian calendar the leap years are divided by four and four hundred if it is ending with double zeros.
The calendars began as a recording of time with the natural cycles such as days, lunar cycles -months and solar cycles – years. Early people, at different periods have created different calendars to keep track of time. Calendars were created to keep track of time and important natural events that may recur in the future.
It is not possible to divide natural cycles evenly into fixed number of days. The lunar cycle does not fit in to an even number of days. Solar year is not equal to particular number of lunar cycles. The word month came from the words moon and ‘th’. Early people made their calendar with the synchronization of lunar cycle. These calendars consisted of months with 29 and 30 days with occasional addition of leap month to synchronize with the solar year, few of the examples are Chinese and Jewish calendars. The ancient Egyptian calendars were created with the solar cycle and did not synchronize with lunar cycles. Ancient Egyptian calendars are credited with the first calendars to have twelve months.
The astronomers use number of days to arrive at calculations. For example an eclipse of a double star is calculated by adding 1583.6 days from the previous eclipse. Julian calendar began at noon on Monday the 1st of January of 4713 BC. All the historical and astronomical observe positive Julian day numbers. The periods and evens can be arrived at by adding and subtracting the number of Julian days.
The Hebrew –or Jewish calendar is ‘luni-solar calendar’. The Hebrew calendar tries to maintain synchronization between months and moon’s alignment with months and season.
The Mayans used three calendars. These calendars had cycles of days with different lengths. The Long Count was used for historical purposes, the Tzolkin was used for religious purposes and the Haab was used for civil purposes. These calendars did not synchronize with sun or moon. Mayan calendars used serial counting of days.
The ancient Indian calendar was lunar based, it contain twelve months. The civil calendar is commonly used now. In the civil calendar the first month is Caitra and the months contain 30 and 31 days. The leap year occurs exactly as Gregorian calendar; hence both have identical accuracy and remain synchronized.
Concept of Time is amazing; it relives memories and brings about imaginations and fantasies from the past and future. A deadline not set for a fixed goal is unimaginable. Calendars help us with the concept of identifying a day to wish and cherish our people and happy events in life.