Q:

# How do you calculate leap years?

A:

The formula for calculating whether a year is a leap year or not is as follows: if a year can be evenly divided by 4 (such as 2012), then it is a leap year unless it can also be evenly divided by 100 (such as 2100). There is one further exception: if a year can be evenly divided by 400 (such as 2000), then it is a leap year.

Know More

## Keep Learning

Credit: Craig Dingle E+ Getty Images

A day on Earth does not really last 24 hours. It takes 23 hours, 56 minutes and 4.1 seconds for the Earth to make a complete rotation. Because of this, the Earth actually rotates about 365.24 times per year. Adding an extra day every four years helps to synchronize the calendar year with the solar year. If the discrepancy were exactly one quarter of a year, then every four years would be a leap year without variation. Since the difference is 0.24 instead of 0.25, one leap year is skipped three times out of every 400 years. Leap year originated in the 16th century, when people realized that the vernal equinox was falling on March 11 instead of March 21. Pope Gregory XIII adjusted the calendar by moving the date ahead by 11 days and instituted the practice of adding an extra day to the calendar every four years.

Sources:

## Related Questions

• A:

The Old Farmer's Almanac lists the dates of recent and upcoming leap years on its website. It also provides the rules to follow in order to independently determine the dates of leap years.

Filed Under:
• A:

Unlike the Gregorian calendar, which counts years infinitely, the traditional Chinese calendar is lunisolar and rotates on a 60-year cycle. This means that the years on a Chinese calendar don't ascend in chronological order, and instead its years are named with words rather than numbers. The year names are based on a combination of one of 10 prefixes, or stems, and one of 12 suffixes, or branches.

Filed Under:
• A:

There are 20 years in a score. The word "score" can be used to mean a set or group of any 20 items, not just years.