Gregorian calendar, New Style calendar - the solar calendar now in general use, introduced by Gregory XIII in 1582 to correct an error in the Julian calendar by suppressing 10 days, making Oct 5 be called Oct 15, and providing that only centenary years divisible by 400 should be leap years; it was adopted by Great Britain and the American colonies in 1752

All Fools' day, April Fools', April Fools' day - April 1; celebrated by playing of practical jokes

April 14, Pan American Day - a day celebrating political and economic unity among American countries

Patriot's Day - the 3rd Monday in April; Massachusetts and Maine celebrate the battle of Lexington and Concord in 1775

Gregorian calendar month - a month in the Gregorian calendar

mid-April - the middle part of April

spring, springtime - the season of growth; "the emerging buds were a sure sign of spring"; "he will hold office until the spring of next year"