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Counting the days between two dates looks trivial but two things trip people up: the way months have different lengths, and leap years. How long a project ran, the gap between two events, a notice period, days of leave — all can go wrong with finger-counting. The tool knows both pitfalls and gives the exact number of days, with weeks and months alongside.
Enter a start and end date, and the exact interval is calculated instantly.
How is it calculated?
How it's calculated
The count is the difference between the two dates' day numbers — independent of month lengths and leap years, giving an exact result. Enter the two dates and the tool returns the days, plus a weeks-and-days and months breakdown.
Why leap years matter
Years with a 29-day February (divisible by 4; except century years not divisible by 400) throw off a rough "years × 365" every time. Over several years two or three leap days accumulate; the tool counts them automatically.
Days / weeks / months
- 1 week = 7 days; results are given with a remainder, like "52 weeks 3 days."
- A "month" here is a calendar month: 15 March → 15 April is one month, regardless of whether it has 30 or 31 days.
- 1,000 days ≈ 2 years 8.9 months; 10,000 days ≈ 27.4 years.
Common uses
- Length of a project or contract period
- Notice periods and deadlines
- Time between two events or milestones
- Age or tenure calculations (raw days)
For counting forward to a future date use a days-until-date calculator; for time since a past date use a days-since-date calculator.
Worked example
From 1 January 2020 to 1 January 2026: exactly 2,192 days pass, including the 29 February of the leap years 2020 and 2024 — that's 313 weeks 1 day, or 72 months. The rough "6 years × 365 = 2,190" would be 2 days short: the two leap days are exactly what a naive multiplication misses, which is why day-number differencing is the reliable method.
FAQ
How do I calculate the days between two dates?+
The tool takes the difference between the two dates' day numbers; month lengths and leap years are handled automatically. Just enter the start and end date.
Are leap years included?+
Yes — every 29 February in the range is counted. Years divisible by 4 are leap years; century years are leap only if also divisible by 400 (2000 is, 2100 is not).
How many years is 1,000 days?+
About 2 years, 8 months and 26 days. 100 days ≈ 3 months 9 days; 10,000 days ≈ 27.4 years.
Does it include the start and end day?+
The result is the number of full days between the two dates. Whether to count both endpoints depends on your use; for a countdown, a days-until-date calculator frames it that way.
Can I calculate weeks or months instead of days?+
The result includes a weeks-and-days breakdown and a calendar-month count alongside the total days, so you can read the interval in whichever unit you need.
What if the end date is before the start date?+
The interval is the same magnitude regardless of order — the tool returns the absolute number of days between the two dates.