Calculate days between dates, add or subtract days, find ages, and discover weekdays.
The Date Calculator handles two common jobs: finding the exact span between two calendar dates, and adding or subtracting a number of days from a starting date to land on a target date. Pick a start and end date to see the difference expressed in total days (and broken into years, months, and days), or enter one date plus an offset like +90 or -30 to get the resulting date.
It runs entirely in your browser and correctly accounts for leap years, month lengths, and the transition across year boundaries, so you don't have to count on your fingers or fight a spreadsheet formula. It's handy for project deadlines, contract and notice periods, invoice due dates, subscription renewals, warranty windows, and age or anniversary calculations.
Difference mode computes the number of whole days between two dates by converting each date to a day count and subtracting. Because it works from real calendar values, February 29 in leap years and the varying lengths of months (28-31 days) are all handled automatically. For example, from 2026-01-15 to 2026-03-15 the tool reports 59 days, since 2026 is not a leap year and February has 28 days.
The years/months/days breakdown is calendar-aware rather than a flat division: it steps forward from the start date one unit at a time, so '1 month' means the same day of the next month, not a fixed 30 days. Add/subtract mode does the inverse, taking a start date and shifting it by your day offset, rolling over month and year boundaries as needed. A key distinction is inclusive versus exclusive counting: the plain difference between two dates is exclusive (the end date is not counted), so a Monday-to-Friday span is 4 days, while an inclusive count that includes both endpoints would be 5 days.
By default the difference is exclusive, meaning the end date is not counted, so the gap from the 1st to the 10th is 9 days. If your task needs both endpoints counted (for example billing days), use the inclusive option, which adds one to the total.
Yes. Calculations use real calendar dates, so February 29 in leap years and the different lengths of each month are taken into account automatically without any manual adjustment.
The breakdown is calendar-based, where one month means the same day in the next month rather than a fixed 30 days. That is why the same span can read as, say, '2 months and 3 days' while also being a specific total number of days.
Yes. In add or subtract mode, enter a negative offset or choose the subtract option to move backward from your start date and find an earlier date.
It is completely free with no sign-up. All calculations run locally in your browser, so the dates you enter are never uploaded or stored on any server.
No. It works with whole calendar dates only and does not factor in hours, minutes, or time zone offsets, so results are consistent regardless of your location.
Yes. Set the birth or event date as the start and today's date as the end in difference mode, and read the years, months, and days breakdown for an exact age or elapsed duration.