Months Between Dates Calculator

Count whole calendar months between two dates, with the leftover days reported separately.

Inputs

Result

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How to use this calculator

  • Enter the start and end date. Order does not matter.
  • The whole-months number is "fully completed months". The hint shows the leftover days, plus a decimal-months estimate using the Gregorian average month length.

About this calculator

Months are tricky — they are not a fixed length, and "one month after January 31" could reasonably be either February 28 or March 3. This calculator follows the calendar-aware convention used by date-arithmetic libraries: a whole month is counted when you have reached or passed the same day-of-month in a later month. The leftover is reported as days.

Frequently asked

When does the calculator add another whole month?+
When the end date reaches or passes the same day-of-month as the start date. From Jan 15 to Feb 14 is 0 whole months (we have not reached the 15th). From Jan 15 to Feb 15 is 1 whole month.
How are end-of-month edge cases handled?+
If the start is on the 31st and the end month does not have a 31st, the day-of-month comparison still works because the underlying date is unambiguous. The calculator never silently rolls February 31 into March.
Why is the decimal-months figure different from the whole months?+
The decimal figure divides total days by the average Gregorian month length (30.4375). It is good for rough estimation. The whole-months figure is the exact calendar-aware count.
Can I use this to count months until retirement, or months on a project?+
Yes — both directions work, and the calculator handles dates in the past or future identically.
Does the calculator account for time zones?+
No — both inputs are interpreted as UTC dates. Since the inputs are date-only (no time component), time zone is not relevant to the result.

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