A leap year has 366 days. It is also known as an intercalary year or bissextile year. It occurs every 4 years.
In the Gregorian calendar, which is used worldwide, the extra day is added to the shortest month of the year which is February. Hence, February has 29 days instead of 28 days. The 29th day, in February, is called the leap day or intercalary day.
Why do we have a leap year?
In the Gregorian calendar, the common year is 365 days.
The Earth takes 365.242189 days (365 days, 5 hours, 48 minutes, and 46 seconds) to make a complete revolution around the sun.
Hence, there is a need to add the extra 0.242375 days.
Therefore, every 4 years an extra day is added which brings an average of 365.25 days per year, but it is not accurate.
To fix the problem, in centuries divisible by 400, an extra day is added which brings an average of 365.2425 days per year, though not perfect but fairly close.
Hence, a leap year is necessary to keep the calendar aligned with Earth’s revolution around the sun.
Origin of leap year
In 45 B.C. Julius Caesar introduced the Julian calendar.
In the Julian calendar every 4th year, a day was added to the calendar to align with the solar year.
By 1582, the vernal equinox (beginning of spring) was ten days early. Hence, Pope Gregory XII called upon astronomers for a solution.
Astronomers found out that miscalculations during the past 15 centuries have resulted in the fact that there is a 10-day difference between the calendar year and the solar year.
Hence, that year they removed ten days from the calendar. The day after 4th October 1582 was 15th October 1582. This skipping of 10 days brought the calendar into agreement with the solar year.
The new calendar was more accurate than the Julian calendar. It was named the Gregorian calendar in honor of Pope Gregory XII.
In the Gregorian calendar, to keep the calendar and the solar year in agreement, the leap year was omitted 3 times every 400 years. This was done by not counting as leap years the years ending in 2 zeroes unless they can be divided by 400.
How to calculate a leap year
To know whether it is a leap year the following criteria are taken into account. They are:
For non-century years, it is a leap year, if it can be evenly divided by 4.
For example 2008, 2012, 2016 are leap years.
For century years (A century year is a year ending in 00) it is a leap year if it can be evenly divided by 400.
For example 1900, 2100, 2200, 2300 are not leap years.
For example 1600, 2000, 2400, 2800 are leap years.
List of leap years 1800-2400
| 1804 1808 1812 1816 1820 1824 1828 1832 1836 1840 1844 1848 1852 1856 1860 1864 1868 1872 1876 1880 1884 1888 1892 1896 | 1904 1908 1912 1916 1920 1924 1928 1932 1936 1940 1944 1948 1952 1956 1960 1964 1968 1972 1976 1980 1984 1988 1992 1996 2000 | 2004 2008 2012 2016 2020 2024 2028 2032 2036 2040 2044 2048 2052 2056 2060 2064 2068 2072 2076 2080 2084 2088 2092 2096 | 2104 2108 2112 2116 2120 2124 2128 2132 2136 2140 2144 2148 2152 2156 2160 2164 2168 2172 2176 2180 2184 2188 2192 2196 | 2204 2208 2212 2216 2220 2224 2228 2232 2236 2240 2244 2248 2252 2256 2260 2264 2268 2272 2276 2280 2284 2288 2292 2296 | 2304 2308 2312 2316 2320 2324 2328 2332 2336 2340 2344 2348 2352 2356 2360 2364 2368 2372 2376 2380 2384 2388 2392 2396 2400 |
How many days does the leap year have?
A usual calendar has 365 days whereas the leap year has 366 days.
Classic leap year rhyme
Thirty days hath September, April, June, and November; All the rest have thirty-one, Excepting February alone, And that has twenty-eight days clear, And twenty-nine in each leap year. - MOTHER GOOSE