What it does
This calculator finds the exact difference between any two dates: how many whole years, months and days separate them, plus the total span in days and weeks. Enter a start date and an end date in either order — if the start date happens to be later than the end date, the calculator simply swaps them and works out the same gap. Everything runs in your browser; no dates are sent anywhere.
How it works
The difference is broken down the way people actually describe a span of time: full years first, then the leftover whole months, then the leftover days. The complication is that a "month" is not a fixed length — February has 28 or 29 days, while others have 30 or 31. So the calculator subtracts day-from-day, month-from-month and year-from-year, then borrows whenever a column comes out negative.
If the end date's day-of-month is earlier than the start date's, there isn't yet a full month's worth of days, so it borrows the length of the previous calendar month and drops the month count by one. If the months then go negative, it borrows twelve months from the year count. The total-days figure is counted directly between the two calendar dates regardless of the year/month/day breakdown, and total weeks is simply that number divided by seven, rounded down.
Worked example
Take a start date of 2024-01-15 and an end date of 2024-12-25. Subtracting gives 0 years, 11 months and 10 days. In total that is 345 days, which is 49 whole weeks.
Common uses
- Project planning: working out how many days or weeks lie between a start date and a deadline.
- Contracts and notice periods: checking the exact length of a term specified as a date range.
- Events and countdowns: seeing how long until (or since) a wedding, holiday or anniversary.
- Billing and rentals: confirming the number of days covered by a stay, lease or subscription period.
- Historical spans: finding how much time passed between two events, however far apart.
Frequently asked
Does it matter which date I enter first?
No. If the start date is later than the end date, the calculator swaps them automatically and returns the same difference either way.
How many total days are between two dates?
The result line shows a total-days figure alongside the years/months/days breakdown — that is the count of whole calendar days between the two dates, independent of how the years/months/days are broken down.
How are leap years handled?
The calculator borrows the real length of each calendar month when working out the years/months/days breakdown, so a span that crosses 29 February in a leap year is still counted correctly.
Why isn't "one month" always 30 days?
Calendar months vary from 28 to 31 days, so the breakdown counts real months rather than fixed 30-day blocks. That is why two date ranges with the same total number of days can show slightly different month-and-day figures.
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