| Month | Short | Days |
|---|---|---|
| January | Jan | 31 days |
| February | Feb | 28 days in a common year and 29 days in leap years |
| March | Mar | 31 days |
| April | Apr | 30 days |
| May | May | 31 days |
| June | Jun | 30 days |
| July | Jul | 31 days |
| August | Aug | 31 days |
| September | Sep | 30 days |
| October | Oct | 31 days |
| November | Nov | 30 days |
| December | Dec | 31 days |
A year of 366 days in the Gregorian calendar,
occurring every fourth year: the additional day, Feb. 29,
makes up for the time lost annually when the approximate 365¼-day cycle**
is computed as 365 days: a leap year is a year whose number is exactly divisible
by 4, or, in case of the final year of a century, by 400
** The length of a year is (more or less) 365.242196 days