How Did The Calendar Begin?

The ancient Egyptians were the first to measure a year with any exactness. They knew that the best time was right after the Nile overflowed each year and they noticed that between each overflowing the moon rose 12 times. So they counted 12 moonths or months to figure out when the Nile would rise again. But it was not exact enough. At last the Egyptian priests noticed that each year about the time of flood, a certain bright star used to rise before the sun. They counted the days that passed before it happened and that it added up to 365 days, it was 6000 years before. The Egyptians divided a year or 365 days in 12 months of 30 days each and counted 5 days extra at the end of the year. Thus the first calendar was invented.

Eventually the calendar was based on the number of day (that is 365 ¼ days) it takes the earth to go around the sun. The extra quarter of day began to cause of more confusions. Finally in 46B.C Julius Caesar ordered to count an extra day after every fourth year for balancing the confusion and in that way leap year arrived.

In the year 1582 Pope Gregory XIII ordered to keep calendar accurate for all future time and so he ruled that leap year should be skipped in the last year of every century unless that year could be divided by 400. That's why 1900 was not a leap year but 2000 was that. This system is called Gregorian calendar and is now used all over the world for daily purposes.