Date Calculator
Count the days, weeks and business days between two dates, or add and subtract time from any date to find the result.
Date Calculator
Days between
30
Business days
22
Weekends excluded
Weeks
4
Weekend days
8
In years
0y 1m 0d
Calendar accurate
The two dates
- Wednesday, September 2, 2026Wednesday · week 36 · day 245
- Friday, October 2, 2026Friday · week 40 · day 275
- Total days30
- Hours720
- Minutes43,200
The count excludes the start date and includes the end date, which is the convention contracts and shipping estimates both use. If you need both ends counted — “how many days am I away for” — add one.
The link carries the values you entered, so whoever opens it sees the same result. Nothing is stored on our side — the numbers travel in the link itself.
How the date calculation works
Date arithmetic looks trivial and is not. Months have different lengths, leap years are irregular, and "one month later" means something a plain day count cannot express.
Days between two dates
The count above excludes the start date and includes the end date, which is the convention contracts, shipping estimates and interest calculations all use. From 1 March to 8 March is seven days.
If you want both ends counted — "how many days am I away for", where the departure day counts — add one. That is the inclusive count, and the difference between the two conventions is the single most common source of off-by-one errors in date work.
Business days
Business days skip Saturdays and Sundays, and the start date is never counted. Three business days from a Friday is the following Wednesday, not Tuesday: you count Monday, Tuesday, Wednesday.
The calculator does not exclude public holidays, because they differ by country, by state and by industry. A US federal holiday calendar does not apply in the UK, and English bank holidays do not apply in Scotland. Where a deadline genuinely matters, check the applicable calendar and subtract manually.
Adding months: why the result clamps
Adding one month to 31 January gives 28 February (or 29 in a leap year) — not 2 or 3 March. This is called clamping, and it is what every calendar application does and what a contract means by "one month later".
It has a consequence worth knowing: month arithmetic is not reversible. 31 January plus one month is 28 February; 28 February minus one month is 28 January. You do not get back where you started. This is not a bug in the calculator but a genuine property of calendar months, and it is why financial contracts specify their own conventions rather than relying on the intuitive reading.
The calculator applies years and months before days, so "one month and one day from 31 January" resolves as 28 February, then 1 March.
Leap years
A year is a leap year if divisible by 4, except century years, unless divisible by 400. So 2000 was a leap year and 1900 was not — a rule that famously broke a great deal of software written on the assumption that every fourth year qualifies.
The Gregorian calendar year is 365.2425 days against the true solar year of about 365.24219, which is accurate to roughly one day in 3,200 years.
ISO weeks
The week number shown is ISO 8601, where weeks start on Monday and week 1 is the week containing the first Thursday of the year. That is why 1 January 2027 falls in week 53 of 2026 — its Thursday is 31 December 2026. Business and manufacturing planning uses ISO weeks; the US convention of starting weeks on Sunday numbers them differently.
Frequently asked questions
How many days are between two dates?
Enter both dates above. The count excludes the start date and includes the end date, which is the convention contracts and shipping estimates use - 1 March to 8 March is seven days. If you want both ends counted, such as the total days of a holiday including the departure day, add one to the result.
How do I count business days?
Business days exclude Saturdays and Sundays, and the start date is never counted, so three business days from a Friday is the following Wednesday. This calculator does not exclude public holidays, because they vary by country, state and industry. For a deadline that matters legally, check the applicable holiday calendar and adjust.
What is one month after 31 January?
28 February, or 29 in a leap year. Month arithmetic clamps to the last valid day rather than rolling over into March, which is what every calendar application does and what a contract means by "one month later". A side effect worth knowing: this makes month arithmetic non-reversible, since 28 February minus one month is 28 January, not the 31st you started from.
Which years are leap years?
Years divisible by 4, except century years, unless they are also divisible by 400. So 2024 and 2000 were leap years; 1900 and 2100 are not. The exception exists because the solar year is about 365.2422 days rather than 365.25, so a plain every-fourth-year rule drifts by roughly three days every four centuries.
What is an ISO week number?
A standard week numbering where weeks begin on Monday and week 1 is the week containing the first Thursday of the year. It means early January can belong to the previous year’s week 52 or 53 - 1 January 2027 is in week 53 of 2026. Manufacturing, logistics and European business planning use ISO weeks; the US convention of starting weeks on Sunday numbers them differently.
Why does adding a month then subtracting a month not return the same date?
Because month lengths differ and the result clamps to a valid date. 31 January plus one month is 28 February, and 28 February minus one month is 28 January. The information about the original 31st is lost at the clamp. This is a genuine property of calendar arithmetic rather than a calculator quirk, and it is why financial contracts define their own date conventions explicitly.
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