Why Leap Years Exist
A year on Earth is a little longer than 365 days. Leap years are how the calendar catches up, and the rule for them is more precise than "every four years".
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The rule
A year is a leap year if it is divisible by 4, except for years divisible by 100, unless they are also divisible by 400. So 2024 and 2028 are leap years. 1900 and 2100 are not. 2000 was, because it divides by 400. 2027 is a normal year with 365 days.
Why the rule is not just "every four years"
The older Julian calendar assumed a year of 365.25 days, which is a little too long. Over centuries the calendar drifted away from the seasons: the March equinox slipped well before its nominal date of March 21, which also affected the calculation of Easter. The Gregorian reform trims the average year to 365.2425 days by skipping a leap year in three of every four century years.
The 1582 reform
Pope Gregory XIII introduced the new calendar in a papal bull dated February 24, 1582. In the countries that adopted it first, Thursday, October 4, 1582 was followed directly by Friday, October 15. Ten days were dropped to bring the calendar back in line. Other countries switched later. Britain and its colonies changed in 1752, and the same change moved the start of the legal year to January 1.
Next leap years
After 2024 the next leap years are 2028, 2032 and 2036. Note that 2100 will not be one.
Print a 2028 calendar2028 is a leap year, so February has 29 days. Monthly pages or a whole year on one page.
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Sources
Checked on October 15, 2026. We summarize in our own words and only state what these sources support.
- Wikipedia: Gregorian calendar — reform date, leap year rule, average year length, adoption in Britain