Date Difference Calculator
Get the precise difference between two dates as years/months/days plus total days and weeks.
Result
How it is calculated
The two dates are put in order (the earlier one is always the start, so entering them backwards still works) and compared part by part: years = Ty − Fy, months = Tm − Fm, days = Td − Fd. A negative day difference borrows one month and adds the length of the month before the end month; a negative month difference borrows one year. Besides this calendar breakdown the tool reports total days (real elapsed time, rounded down), total weeks (total days ÷ 7, rounded down) and total months (years × 12 + months). The start day counts as day zero, so the end date itself is not added in.
Worked example
From 2024-02-20 to 2025-04-05. Years: 2025 − 2024 = 1. Months: 4 − 2 = 2. Days: 5 − 20 = −15, so borrow a month: months = 1 and days = −15 + 31 (March has 31 days) = 16. The calendar difference is 1 year, 1 month and 16 days, which is 13 months in total. In days: 366 days to 2025-02-20 (the span contains 29 February 2024) plus 44 more gives 410 days, or 58 full weeks.
Common mistakes
- Expecting the end date to be counted too. The result is the number of nights between the dates, so Monday to Tuesday is 1 day, not 2.
- Adding the years/months/days figures to get the total number of days. Use the separate total days value, because months have different lengths.
- Reading total months as an exact figure. It is whole months only; the remaining days are shown separately.
- Worrying about the order of the dates. They are sorted automatically, so the result is never negative and cannot tell you which date is earlier.
About this calculator
This calculator measures the span between two chosen dates, expressing the result in days, weeks, months, or years as needed, and correctly accounts for varying month lengths and leap years along the way. Unlike a simple subtraction of numbers, calendar math has enough irregularities that a dedicated calculator avoids common counting mistakes.
It's used for project planning and deadline tracking, working out how many days remain until an event, checking a contract or notice period length, or figuring out how long ago something happened. It's also a common building block behind other date-based calculators, like age or pregnancy timelines.
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