Question 1

How is the difference between two dates calculated?

Accepted Answer

We compute the calendar-aware difference using the same approach as Excel's DATEDIF and Python's relativedelta: full years first, then full months, then leftover days. Edge cases like Jan 31 → Mar 1 are reported as "1 month, 1 day" (because Jan 31 + 1 month clamps to Feb 29 in a leap year), not "0 months, 30 days". All math runs in UTC so daylight-saving transitions never produce off-by-one results.

Question 2

Are leap years handled correctly?

Accepted Answer

Yes. Feb 29 is accepted as a valid input date only in leap years (years divisible by 4, excluding centuries that aren't divisible by 400 — so 2000 ✅, 1900 ❌). Adding 1 year to Feb 29 lands on Feb 28 in non-leap years; adding 4 years rolls back to Feb 29.

Question 3

How are business days counted?

Accepted Answer

We count Monday through Friday inclusive of both endpoints, using a closed-form formula (no per-day loop, so multi-decade ranges are still instant). Holidays you provide are subtracted only when they fall on a weekday inside the range — a holiday that lands on a Saturday or outside your range is ignored.

Question 4

Can I share a specific calculation?

Accepted Answer

Yes — the URL updates as you change inputs (mode, dates, durations, holidays). Click "Copy share link" to copy the current URL. All inputs round-trip exactly.

Date Calculator

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