Months of the Year

The 12 months in the table above don’t all have the same number of days, which trips people up more often than you’d expect. Seven months — January, March, May, July, August, October, and December — have 31 days. Four months — April, June, September, and November — have 30. February is the odd one out with just 28 days most years, and 29 during leap years.

Remembering the pattern

Generations of schoolchildren have relied on a rhyme: “Thirty days hath September, April, June, and November; all the rest have thirty-one, except February alone, which has twenty-eight days clear, and twenty-nine in each leap year.” The knuckle trick works too — count along the knuckles and grooves of a closed fist, knuckles being 31-day months and grooves being the shorter ones. Both are shortcuts precisely because the lengths aren’t evenly distributed.

Why the lengths are uneven

The unevenness traces back to the Roman calendar, which was adjusted and re-adjusted over time — including Julius Caesar’s reform that produced the Julian calendar — before evolving into the Gregorian calendar most of the world uses today. The month names carry their own history: September through December come from the Latin words for seven, eight, nine, and ten, positions they held before January and February were added to the front of the year.

Leap years

Leap years exist to correct for the fact that Earth’s orbit around the Sun takes about 365.25 days rather than an even 365, so an extra day is added to February roughly every four years to keep the calendar aligned with the seasons. The precise rule: divisible by 4, except century years, which must be divisible by 400.

Month-by-month detail

Each month has its own page with day count, season, quarter, holidays, and origin — starting with January and running through the year. To see which month it is right now, use what month is it. For where today sits in the year, see what day of the year it is.

Month numbers and abbreviations

Two-digit month numbers are what dates like 2026-04-15 use. The three-letter form is the usual short abbreviation; AP style, used by many newspapers, abbreviates only seven months when they appear with a date and spells out March to July.