Why do people born on February 29th have their birthdays only once every four years? How come? Why?

February 29th is the 60th day of leap year in Gregorian calendar, and there are 306 days before the end of the year. February 29th will not appear in general years, but only in leap years. Usually, leap years are divisible by 4.

February 29th is a very special day. It is human beings who make up a little more for 365 days a year and make up one day every four years. The julian calendar formulated by the ancient Romans in 46 BC did this for the first time.

Therefore, if the birthday is on February 29th, it can only be celebrated once in a leap year, that is, once every four years.

Extended data:

Reasons for leap years

The period of the earth's orbit around the sun is 365 days, 5 hours, 48 minutes and 46 seconds (365.438+09 days), which is the tropic of cancer. The Gregorian calendar has an average of only 365 days a year, which is about 0.2422 days shorter than the tropical year, and the remaining time is about one day every four years. So 1 day is added at the end of February of the fourth year, making the calendar year of that year 366 days, and this year is a leap year.

The current Gregorian calendar has 97 leap years every 400 years. According to a leap year every four years, it will count as 0.0078 days per year on average, so after 400 years, it will count as 3 days. So every 400 years, three leap years will be reduced.

Therefore, the Gregorian calendar stipulates that when the year is a whole hundred, it must be a multiple of 400 to be a leap year; It is not a century year with multiples of 400, and even a multiple of 4 is not a leap year.

This is what is usually said: jump in four years, not jump in a hundred years, and jump again in four hundred years. For example, 2000 is a leap year, and 2 100 is a normal year.

Baidu Encyclopedia-February 29th