Date Calculator

Adding or subtracting a period from a date sounds trivial until months are involved, and this does it with calendar arithmetic rather than day counting: month and year steps land on the same day number wherever one exists. Enter a starting date, the days, months or years to add or subtract, and read the resulting date. It answers everyday questions with real consequences — when a ninety-day notice period ends, what date a warranty expires, when a document dated today falls due. The edge cases are where the arithmetic gets opinionated, and it is worth knowing which convention is applied. Adding one month to 31 January has no exact answer, so the result clamps to the last valid day of February rather than spilling into March. Adding a year to 29 February similarly falls back to 28 February in a non-leap year.