How many months in the calendar year have 31 days?

A month is a unit of time, used with calendars, which is approximately as long as a natural period related to the motion of the Moon; month and Moon are cognates. The traditional concept arose with the cycle of Moon phases; such months (lunations) are synodic months and last approximately 29.53 days. From excavated tally sticks, researchers have deduced that people counted days in relation to the Moon's phases as early as the Paleolithic age. Synodic months, based on the Moon's orbital period with respect to the Earth-Sun line, are still the basis of many calendars today, and are used to divide the year.

There are seven months in the calendar year that have a total of 31 days. The months and days are:

1 January 31 days

2 February 28 days (29 in leap years)

3 March 31 days

4 April 30 days

5 May 31 days

6 June 30 days

7 July 31 days

8 August 31 days

9 September 30 days

10 October 31 days

11 November 30 days

12 December 31 days