LEAP YEARA leap year (or intercalary year) is a year containing one or more extra days in order to keep the calendar year synchronised with the astronomical or seasonal year.
For example, February would have 29 days in a leap year instead of the usual 28. Seasons and astronomical events do not repeat at an exact number of full days, so a calendar which had the same number of days in each year would over time drift with respect to the event it was supposed to track. By occasionally inserting (or intercalating) an additional day the drift can be corrected. A year which is not a leap year is called a common year.
In the Gregorian calendar, the current standard calendar in most of the world, most years that are divisible by 4 are leap years. In a leap year, the month of February has 29 days instead of 28. Adding an extra day to the calendar every four years compensates for the fact that a solar year is almost 6 hours longer than 365 days.
However, some exceptions to this rule are required since the duration of a solar year is slightly less than 365.25 days. Years which are divisible by 100 are not leap years, unless they are also divisible by 400, in which case they are leap years.[1][2] For example, 1600 and 2000 were leap years, but 1700, 1800 and 1900 were not. Going forward, 2100, 2200, 2300, 2500, 2600, 2700, 2900, and 3000 will not be leap years, but 2400 and 2800 will be. By this rule, the average number of days per year will be 365 + 1/4 − 1/100 + 1/400 = 365.2425, which is 365 days, 5 hours, 49 minutes, and 12 seconds.
The Gregorian calendar was designed to keep the vernal equinox on or close to March 21, so that the date of Easter (celebrated on the Sunday after the 14th day of the Moon that falls on or after 21 March) remains correct with respect to the vernal equinox.[3] The vernal equinox year is about 365.242374 days long (and increasing), whereas the average year length of the Gregorian calendar is 365.2425.
The marginal difference of 0.000125 days means that in around 8,000 years, the calendar will be about one day behind where it is now. But in 8,000 years, the length of the vernal equinox year will have changed by an amount which cannot be accurately predicted (see below). Therefore, the current Gregorian calendar suffices for practical purposes, and Herschel's correction (making 4000 AD not a leap year) will probably not be necessary.
Calendar Companies! Name that day!
Leap Year Day is the name of February 29. Just like New Year's Day is the name of January 1. Leap Day represents how cool the calendar system is.
In the Gregorian calendar, the current standard calendar in most of the world, most years that are divisible by 4 are leap years. In a leap year, the month of February has 29 days instead of 28. Adding an extra day to the calendar every four years compensates for the fact that a solar year is almost 6 hours longer than 365 days.
However, some exceptions to this rule are required since the duration of a solar year is slightly less than 365.25 days. Years which are divisible by 100 are not leap years, unless they are also divisible by 400, in which case they are leap years.[1][2] For example, 1600 and 2000 were leap years, but 1700, 1800 and 1900 were not. Going forward, 2100, 2200, 2300, 2500, 2600, 2700, 2900, and 3000 will not be leap years, but 2400 and 2800 will be. By this rule, the average number of days per year will be 365 + 1/4 − 1/100 + 1/400 = 365.2425, which is 365 days, 5 hours, 49 minutes, and 12 seconds.
The Gregorian calendar was designed to keep the vernal equinox on or close to March 21, so that the date of Easter (celebrated on the Sunday after the 14th day of the Moon that falls on or after 21 March) remains correct with respect to the vernal equinox.[3] The vernal equinox year is about 365.242374 days long (and increasing), whereas the average year length of the Gregorian calendar is 365.2425.
The marginal difference of 0.000125 days means that in around 8,000 years, the calendar will be about one day behind where it is now. But in 8,000 years, the length of the vernal equinox year will have changed by an amount which cannot be accurately predicted (see below). Therefore, the current Gregorian calendar suffices for practical purposes, and Herschel's correction (making 4000 AD not a leap year) will probably not be necessary.
Calendar Companies! Name that day!
Leap Year Day is the name of February 29. Just like New Year's Day is the name of January 1. Leap Day represents how cool the calendar system is.
rIt's the day that celebrates the calendar! So come on calendar companies! Put the name of February 29 in ink on every February 29!
It's Leap Day, simple as that. And it's about time -- literally!
Click (here) to find out more about Leap Year!
Why Leap Years Are Used
It's Leap Day, simple as that. And it's about time -- literally!
Click (here) to find out more about Leap Year!
Why Leap Years Are Used
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