Date Duration Calculator

Enter two dates and get the duration in days, business days, weeks, months, and years. Business days mode excludes weekends (Sat + Sun) but does not know about US or international holidays.

Processing happens entirely in your browser. Nothing is uploaded.

Start Date

End Date

Business-days mode excludes weekends only. Public and observed holidays vary by country, state, and industry — this calculator doesn't know about them.

Duration

Common conventions

Days: the calculator uses inclusive-end date arithmetic — if you enter start = 2026-01-01 and end = 2026-01-02, you get 1 day (not 2). This matches how deadlines and rental periods are typically counted.

Business days: weekdays only (Monday through Friday). Excludes Saturday and Sunday. Does not exclude holidays — you'll need to subtract those yourself. In the US, federal holidays are typically 10-11 per year; state and industry-specific holidays add more.

Months/years: calendar-based, not fixed 30-day or 365-day. From 2026-01-15 to 2026-03-15 is exactly 2 months. Partial months are shown as remainder days.

Time zones and DST

Dates are treated as local calendar days — DST changes don't affect the count because a day is always a day, regardless of whether it's 23 or 25 hours long.