Leap Year (yr (366))

CalendarCurrent unit

A calendar year of exactly 366 days, with the leap day on February 29.

1 leap year = 31,622,400 seconds (exactly).

About the leap year

Julius Caesar's edict, effective 1 January 45 BC, turned the Roman calendar into a solar one with an extra day every fourth year. The English phrase is thought to come from weekdays: a fixed date normally moves ahead one weekday each year, but after a leap day it moves two, appearing to leap over one. The extra day is 29 February, used since about the fifteenth century, and British law recognized it formally in 1750.

A leap year has 366 days, or 31,622,400 seconds. The Gregorian rule, which now governs most of the world, makes a year a leap year when divisible by four, except century years that are not divisible by 400. So 2000 was a leap year and 1900 was not. That leaves 97 leap years in each 400-year cycle and a mean year of 365.2425 days, close to the tropical year.

Sources: Wikipedia: Leap year; Wikipedia: Common year

Leap Year conversion chart

1 leap year expressed in every other time unit:

More Calendar units

• week (time)
• month (time)
• year (time)
• common year (time)
• decade (time)
• century (time)
• millennium (time)

All Calendar units

Browse all time units.