Date Calculator
Add or subtract days, weeks, months and years from a date.
Runs entirely in your browser — nothing you enter is uploaded or sent to a server.
Business-day mode skips Saturdays and Sundays only — it knows nothing about public holidays, which differ by country, state and year. If a deadline depends on holidays, check a local calendar as well. Read our full disclaimer.
About this tool
Give it a starting date and an amount of time and it tells you where you land, along with the weekday — useful for deadlines, notice periods, warranty windows and anything counted in weeks. It handles the awkward part properly: adding a month to the 31st of a month clamps to the last day of the shorter one, so 31 January plus a month is 28 February rather than rolling on into March. Business-day mode counts only Monday to Friday, stepping over weekends instead of counting them, which is how notice periods and delivery estimates are usually written. This is the companion to the Date Difference tool — that one measures the gap between two dates you already have, this one finds the date at the end of a gap.
Example
Add 90 days to 8 August 2026 and you get 6 November 2026, a Friday. Ask for 90 business days instead and it's 14 December 2026, because eighteen weekends are stepped over.
How to use
- 1Pick a starting date — today is filled in for you.
- 2Choose whether you're adding or subtracting.
- 3Enter the amount in years, months, weeks or days — or switch to business days.
- 4Read the resulting date and its weekday.
Features
- Add or subtract years, months, weeks and days together.
- Business-day mode that skips Saturdays and Sundays.
- Month arithmetic clamps to the end of a short month instead of overflowing.
- Shows the weekday you land on, and the total days elapsed.
Frequently asked questions
What is one month after 31 January?
28 February, or 29 February in a leap year. There is no 31 February to land on, so the standard convention — and the one this tool follows — is to clamp to the last day of the target month. Some tools overflow instead and give you 2 or 3 March, which is why the same question can produce two different answers online.
How are business days counted?
Only Monday to Friday count, and weekends are stepped over rather than counted. Five business days from a Monday lands on the following Monday, not on Saturday. Public holidays are not included — they vary too much by place to guess.
In what order are the units applied?
Years and months first, clamped together, then weeks and days added as plain 24-hour spans. That order matters: applied the other way round, the answer would depend on which box you happened to fill in first, which is not something a calculator should do.
How is this different from the Date Difference tool?
They answer opposite questions. Date Difference takes two dates and tells you the gap; this takes one date and a gap and tells you the other date. If you already know both dates, you want the other tool.
Does it handle time zones?
It works in whole calendar days and treats every date as a plain calendar date, with no time of day and no zone conversion. That's what you want for deadlines and notice periods — a date shouldn't shift because you opened the page while travelling.
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