Date Add / Subtract Calculator
Add or subtract days, weeks, months or years from any date to find a future or past date. Perfect for deadlines, due dates and planning. Free, private, instant.
Last reviewed by the Radiatus Cloud team
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Add or subtract time from a date
Finding a date a certain number of days, weeks, months or years from another is a common need with a fiddly calculation. This calculator adds or subtracts those units from any date to find the resulting date.
Why date arithmetic is not simple
Adding days is easy until a month or year boundary, and adding months is trickier still, because months have different lengths, so a month after 31 January is not simply the 31st of February. Leap years complicate adding years. Doing this by hand invites off-by-one and boundary errors. The calculator handles the calendar correctly, so adding or subtracting any period gives the right date, which is what you need for deadlines, planning, and working out dates in the future or past.
A calculation, not advice
It runs entirely in your browser, so nothing you enter is uploaded and it works without an account, keeping your figures on your own machine.
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Frequently Asked Questions
What can it add or subtract?
Days, weeks, months or years, forward or backward from any starting date, to find the resulting date.
Why is adding months tricky?
Because months have different lengths, so a month after the 31st is ambiguous, and the calculator resolves it correctly rather than overflowing.
Does it handle leap years?
Yes. It accounts for the calendar including leap years when adding or subtracting periods, giving the correct resulting date.
What is it useful for?
Deadlines, planning, and finding a date a set period before or after a known one, without error-prone manual counting.
Is my data uploaded?
No. The calculation runs entirely in your browser.
Privacy & Security
All processing happens locally in your browser — nothing is uploaded.
How to Use
Pick a start date, choose to add or subtract, and enter the amount and unit.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.
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