Date Calculator

How the numbers are defined

Total days is the plain distance between the two dates — the number of midnights you cross walking from one to the other. Order doesn't matter; you always get a positive count (same date = 0).

Years / months / days is the calendar breakdown, the same one you use for ages: from 2024-02-29 to 2025-03-01 is 1 year and 1 day, because one year after 2024-02-29 is 2025-02-28 (the clamp below) and one day remains. This breakdown always adds back exactly: start + years + months + days lands on the end date.

Weekdays counts Mondays through Fridays in the half-open stretch from the earlier date (inclusive) to the later date (exclusive) — start counts if it's a weekday, the end doesn't. Saturday and Sunday never count, and the number stays the same when you swap the dates.

Add / subtract follows real calendar rules. Adding one month to January 31 gives February 28 (or 29 in a leap year) — a result that simply doesn't exist is clamped to the last day of the target month, and the page tells you when that happens. Years work the same way, so four years after a February 29 is February 28. Subtracting works symmetrically from the same start date.

ISO week is the official ISO 8601 week number: weeks start on Monday, week 1 is the one containing the first Thursday of the year, and early January can belong to week 52 or 53 of the previous year. The tool shows the week's actual year alongside it.

All arithmetic is done in plain calendar days with no time zones, so a date means the same thing everywhere. The today button uses your device's clock. Nothing leaves your browser — there are no network requests at all.