How Many Days Are in a Month

Seven months have 31 days (January, March, May, July, August, October and December) and four have 30 days (April, June, September and November). February has 28 days, or 29 in a leap year, which makes the calendar year 365 or 366 days long.

A year is a leap year when it divides by 4, but a year ending in two zeroes only counts if it also divides by 400. That is why February 1900 had 28 days while February 2000 had 29, and the next skipped leap year is 2100.

Use the knuckle rule: name the months along the knuckles and hollows of a closed fist, starting with January on the first knuckle. Every month that lands on a knuckle has 31 days and every month that lands in a hollow has 30 — February being the single exception.