Date Duration Calculator
Diff dates, add/subtract durations, or countdown — with totals, business days, and copy-ready code snippets.
Result
Target is in the past.
Breakdown
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Business days count Mon–Fri only; public holidays are not excluded. Day-level diffs across DST boundaries can differ from raw millisecond totals — calendar fields above use local date parts.
Code snippets
About this tool
Calendar date math is trickier than subtracting two timestamps. Months have different lengths, so "3 months" is not a fixed number of days. Daylight saving time can make two local midnights fewer than 24 hours apart in raw milliseconds.
This calculator shows calendar breakdown, totals, and business days (Mon–Fri only — public holidays are not excluded). Add/subtract mode chains years through minutes onto a base date. Countdown mode shows time left to a target.
Snippets cover vanilla Date, date-fns, and Temporal so you can paste working code. Dates sync to the URL for sharing. Everything runs in your browser.