April is the fourth month of the year in the Gregorian calendar, the fifth in the early Julian, the first of four months to have a length of 30 days, and the second of five months to have fewer than 31 days. April is commonly associated with autumn in parts of the Southern Hemisphere and spring in parts of the Northern Hemisphere. It is the seasonal equivalent to October in the Southern Hemisphere and vice versa. The Romans gave this month the Latin name Aprilis but the derivation of this name is uncertain.

Months of the Year

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. Researchers have deduced that people counted days in relation to the Moon's phases from excavated tally sticks as early as the Paleolithic age.