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Q:

# How often does a leap year occur?

A:

A leap year occurs almost every four years on February 29. In order for a year to be a leap year, it must be evenly divisible by 4; however, if the year is evenly divisible by 100, it is not a leap year unless it is also evenly divisible by 400, in which case it is a leap year. This means that 1700, 1800 and 1900 were not leap years, but 2000 was a leap year.

Know More

The actual length of a year, defined by the amount of time it takes for the Earth to make a complete circle around the sun, is 365.24 days. The Gregorian calendar normally contains 365 days in a year. This is about a quarter of a day less than the actual number of days in a year, so an extra day is added to the calendar almost every four years to correct the situation.

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## Related Questions

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Calendar dates repeat regularly every 28 years, but they also repeat at 5-year and 6-year intervals, depending on when a leap year occurs within those cycles, according to an article from the Sydney Observatory. Repeating calendar dates are also affected by the adjustments made for leap years at the end of each century.

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February only has 28 days to allow for the other months to have 29 or 31 days, according to the rules set by the Roman king Numa Pompilius. The original Roman calendar had 10 months and began with March. After the reorganization, February was used for purification rituals.

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In 46 B.C., Julius Caesar created leap years in the Julian calendar to accommodate his astronomer's estimate that one year was 365.25 days. By adding one day to the calendar every four years, the calendar would align with the seasons.