Date Calculator
Two tools in one: count the exact days between two dates (with weeks and a calendar breakdown), or add and subtract days from a date to find a deadline. Leap years and month lengths are handled by walking the real calendar.
How dates are counted
Days between dates is a plain count of calendar days from the start date up to, but not including, the end date — the same convention banks and courts use for day counting. From January 1 to January 31 is 30 days, not 31.
The years/months/days breakdown can't be computed by dividing by 30, because months have 28–31 days. Instead the calculator walks the calendar: full years first, then full months, then leftover days — borrowing real month lengths when needed. Adding days is the reverse walk: every calendar day counts, weekends and holidays included.
Worked examples
Example 1: days until Christmas
How many days from November 7, 2026 to December 25, 2026?
- Days left in November (end of month minus the 7th).30 − 7 = 23 days
- Add the December days before the 25th.23 + 24 = 47… check: + Dec 1–25 exclusive = 23 + 25 = 48
- Or count directly: Nov 7 → Dec 25.48 days = 6 weeks 6 days
48 days (6 weeks and 6 days).
Example 2: a 90-day deadline
A contract signed November 7, 2026 gives 90 days. What's the deadline?
- Days left in November.30 − 7 = 23 (through Nov 30)
- Subtract December.90 − 23 − 31 = 36 days into the next period
- Subtract January, land in February.36 − 31 = 5 → February 5, 2027
The 90th day is February 5, 2027 (a Friday).
Example 3: why Feb 1 → Mar 1 isn't "30 days"
Days between February 1 and March 1 in 2024 vs 2025.
- 2024 is a leap year: February has 29 days.2024-02-01 → 2024-03-01 = 29 days
- 2025 is a common year: February has 28 days.2025-02-01 → 2025-03-01 = 28 days
29 days in 2024, 28 days in 2025 — same "one month", different day counts.
FAQ
Does the count include both the start and end date?+
The start date counts, the end date doesn't (exclusive counting) — Monday to Friday is 4 days. If you need both ends included, as for medication courses or hotel nights vs days, add 1 to the result.
Are weekends and holidays counted?+
Yes — this calculator counts every calendar day. Business-day counting (skipping weekends and public holidays) is a different calculation; a business-days mode is on the roadmap.
How does the calculator handle leap years?+
By using the real calendar rather than a 365-day approximation. Years divisible by 4 are leap years, except century years not divisible by 400 — so 2024 and 2000 are leap years, 1900 and 2100 are not.
Why does the years/months/days breakdown look different from days ÷ 30?+
Because months aren't 30 days long. The breakdown walks the actual calendar, so "1 year 2 months 5 days" means full calendar years and months, borrowing each month's true length. Dividing total days by 30 or 30.44 gives only an estimate.
Can I calculate weekdays — what day of the week a date falls on?+
Yes — the add/subtract mode always names the weekday of the resulting date, e.g. "Friday, February 5, 2027".
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