A leap year (English: Leap year) is a year that has one additional day in order to adjust the calendar to an astronomical year. In one year, it does not exactly consist of 365 days, but 365 days 5 hours 48 minutes 45.1814 seconds. If this is ignored, then every four years will be almost 1 day short (to be exact 23 hours 15 minutes 0.7256 seconds). So to compensate for this, every 4 years (a year divisible by 4), is given 1 extra day: February 29. However, since 5 hours 48 minutes 45.1814 seconds is less than 6 hours, years that are divisible by 100 (such as 1900) are not leap years, unless they are divisible by 400 (such as 2000).
There is an easy algorithm to determine whether a year is a leap year or not as follows:
If the number of the year is divisible by 400, then the year is definitely a leap year.
If the number of the year is not divisible by 400 but is divisible by 100, then the year is definitely not a leap year.
If the number of the year is not divisible by 400, not divisible by 100 but divisible by 4, then the year is a leap year.
If the year number is not divisible by 400, is not divisible by 100, and is not divisible by 4, then the year is not a leap year. Leap Years according to this definition have existed since the launch of the Gregorian calendar (1582).
Pseudocode to determine whether a year is a leap year or not:
Chinese Calendar as well as Jewish Calendar
The Chinese and Jewish calendars use 19 years for the 7 months of the 19 sun.
In a leap year the Chinese calendar adds 1 month (30 days) called Lun (simplified Chinese: ; traditional Chinese: ; pinyin: rùn'èryuè) , while the Jewish one month (30 days) in the Adar year. The leap in the zodiac calculation is the Rat, the Dragon, and the Monkey.
The Hijri calendar uses the basis of the moon's revolution with respect to the sun. The moon revolves in 29.5 days, which is equal to the length of the moon's rotation.
The length of time the moon revolves around the earth is 29.5 days rounded up to 29 and 30 days. So that in one month in the Hijri calendar there are 29 or 30 days.
In addition to revolving around the earth, the moon also revolves around the sun along with the Earth.
In 29.5 days or 1 month revolves around the earth at that time the position of the Earth also evolves with respect to the sun for 29.5 days or we call it 1 month. So the length of time the moon around the sun is 12 months or 29.5 days times 12 354 days.
While in a leap year the number in 1 year in the Hijri calendar is 355 days. In a leap year the Hijri calendar adds 1 day (30 days) to the month of Dzulhijjah.