How this calculator works
The earlier date is treated as the starting anchor. Whole calendar months are counted first, clamping the same day to a shorter month’s final day, then the remaining days are counted. Whole weeks are elapsed days divided by seven, rounded down. Dates are handled in UTC without time-of-day or daylight-saving adjustments.
The formula
Calendar months = largest whole-month shift from earlier date not after later date
Remaining days = days after that clamped anniversary
Years = whole months / 12, rounded down.A quick example
From 31 January 2024 to 29 February 2024 the interval is 1 calendar month and 0 days, with 29 total days and 4 complete weeks.
How to use this calculator
- Enter the two dates, in either order.
- Calculate the calendar interval.
- Compare years/months/days with elapsed days, which answer a different question.
A few common questions
Does reversing the dates change the size?
No. Only the date-order label changes.
How are month ends counted?
The anchor day is clamped to the last valid day of a shorter month.
Is the end date counted as an extra day?
No. This measures elapsed days; use Days Between Dates for an inclusive counting option.