What this calculator does
This tool handles common month-based date math: adding months to a date, subtracting months from a date, or finding the total number of months between two dates.
How it works
When adding or subtracting months, the calculator shifts the calendar month while keeping the day of month as close as possible, capping it to the last valid day if the target month is shorter (for example, adding one month to January 31 lands on the last day of February). When finding months between two dates, it counts full calendar months elapsed and also shows the approximate total days and a years-plus-months breakdown.
This calculator uses standard calendar (Gregorian) month lengths and does not account for time zones.
Last reviewed August 2026