Assumptions
- Gregorian calendar; dates only, no time of day or time zone.
- Weekday count excludes Saturday and Sunday only.
- Adding months or years clamps to the last day of the target month when the day does not exist (same as Excel EDATE).
How it is calculated
- Total days = end − start. Both dates are normalized to noon UTC before subtracting, so daylight-saving changes never produce off-by-one errors. "Include end date" adds 1.
- Years / months / days: add whole months to the start date as long as the result does not pass the end date, split into years and months, then count remaining days.
- Weeks = total days ÷ 7, remainder shown as days.
- Weekdays = number of days in the range whose weekday is Monday–Friday.
- Add / subtract: days and weeks are added directly; months and years move the month number and clamp to month-end.
Examples
| Situation | Input | Result |
|---|---|---|
| Tenure at a job | 2021-03-02 → 2026-09-06 | 2,014 days = 5 y 6 mo 4 d |
| Vacation days | 2026-08-03 → 2026-08-07, include end | 5 days, 5 weekdays |
| Net-30 invoice due | 2026-09-06 + 30 days | 2026-10-06 (Tuesday) |
| One-year lease | 2026-02-28 + 1 year | 2027-02-28 |
| Month-end billing | 2026-01-31 + 1 month | 2026-02-28 (clamped) |
Common mistakes
- Don\'t mix inclusive and exclusive counts. "3 nights" is exclusive; "4 days on site" is inclusive. Same dates, results differ by 1.
- Excel subtraction (=B1-A1) equals the exclusive count. Add 1 for inclusive.
- "Same day next month" may not exist. Starting on the 31st rolls to the 28th/29th/30th in shorter months — check recurring payment dates.
- Dates before 1582 (Julian calendar) are not supported.
FAQ
Should I include the end date?
Include it when you are counting a duration that covers both ends — days of leave, days on site, the length of a rental. Leave it unchecked for an interval ("how many days until"). Sept 1 to Sept 3 is 3 days inclusive, 2 days exclusive.
What is one month after January 31?
February has no 31st, so this tool returns the last day of February (28, or 29 in a leap year) — the same behavior as Excel's EDATE. If a contract says "the last day of each month" that is correct; if it says "the 31st", most businesses also roll to month-end when the day does not exist.
Why do other sites give a different years/months/days result?
Month-end edge cases (Jan 31 → Mar 1) can be reported as "1 month 1 day" or "1 month −2 days" depending on method. This tool adds whole months to the start date without passing the end date, then counts the leftover days, so the parts are always non-negative. The total day count is the same either way.
Does "weekdays" exclude public holidays?
No — it excludes Saturdays and Sundays only. A separate business-day calculator handles U.S. federal holidays.
Is anything I type saved or sent anywhere?
No. The calculation runs in your browser only. Refreshing the page clears it.