Date Calculator — days between two dates online
Work out how many days, weeks, months or years lie between two dates, or add and subtract time from a date. Free online date difference calculator.
Use a negative number to go backwards
About the Date calculator tool
Counting days across a calendar by hand is more error-prone than it feels, because months have four different lengths and February changes. Working out a notice period, a project deadline, a visa validity window, a payment due date or how long is left until an event all involve the same arithmetic, and getting it wrong by a day or two has real consequences when a contract or an immigration rule is attached to the answer.
The subtlety that catches everyone is whether both endpoints count. There are six days between the 1st and the 7th if you subtract, but seven dates in that range if you include both — and legal and administrative deadlines vary in which they mean. A thirty-day notice period may run from the day after service rather than the day of it. When the deadline matters, read the wording carefully rather than assuming, because the two readings differ by exactly the day that tends to matter.
Months are the other place intuition fails, and it is why the tool reports days as well. A month is not a fixed quantity, so adding one to 31 January has no unambiguous answer — different systems give 28 February, 2 March or 3 March, all defensible. Anywhere precision counts, count in days. Reserve months and years for describing a duration to a person rather than for computing a deadline.
Knowing the weekday of the result is more useful than it first appears. A deadline that lands on a Saturday will not be processed until Monday, a delivery promised in ten days may miss a weekend, and an appointment calculated correctly can still be impossible. Seeing the day of the week alongside the date catches that immediately, before you commit to a plan built on it.
How it works
Enter the dates
Pick a start and an end date to measure the gap between them, in days, weeks, months and years.
Or add and subtract
Add a number of days to the start date instead, using a negative number to count backwards from it.
Check the weekday
The resulting day of the week is shown, so a deadline landing on a weekend is obvious straight away.
Frequently asked questions
- Does the count include both the start and end dates?
- The difference is calculated by subtraction, so from the 1st to the 7th is six days. If your situation counts both endpoints — as many notice periods and rental agreements do — add one. Which convention applies is determined by the contract or regulation involved, so check the wording when the answer carries consequences.
- How are leap years handled?
- Automatically and correctly. A year is a leap year if divisible by four, except centuries, which must also be divisible by 400 — so 2000 was a leap year and 1900 was not. Any range spanning 29 February includes it. This is the rule that manual counting most often gets wrong over multi-year spans.
- Why is the number of months approximate?
- Because months have between 28 and 31 days, so the answer depends on which months a range crosses. Adding one month to 31 January has no unambiguous result — different systems produce 28 February, 2 March or 3 March. Use days whenever precision matters and months only for describing a duration conversationally.
- Can it count only working days?
- It counts calendar days, including weekends and holidays. Business-day calculation depends on which country you are in, which holidays it observes, and whether the organisation involved recognises them — none of which can be assumed. The weekday of the result is shown so you can spot when a deadline falls awkwardly and adjust.
- Does it account for time zones?
- Dates are treated as plain calendar dates without a time or a zone, which is what you want for deadlines, birthdays and notice periods. If you need an exact elapsed duration across time zones, including the hour a daylight-saving change adds or removes, that is a different calculation and needs timestamps rather than dates.
- How do I count backwards from a deadline?
- Use the add-days field with a negative number and the start date set to your deadline. That is the reliable way to answer questions like when a thirty-day notice must be served, or when to begin a process that has to complete by a fixed date — and it shows you the weekday you would need to act on.
- Is anything I enter sent anywhere?
- No. The calculation runs in your browser tab and no dates are transmitted, stored or logged. That is worth knowing given what people actually calculate here — visa expiries, medical dates, contract terms and notice periods are all information that has no business being recorded by a website.