Date & Time
Add / Subtract Days Calculator
Calculate a date before or after a chosen number of days, weeks, months, or years.
August 30, 2026 + 30 days = September 29, 2026
Weekday
Tuesday
Date input format
2026-09-29
Month/year policy
Clamps to final valid day
Operation
Add time
About This Tool
Use this date calculator to find the calendar date before or after a starting date. It supports day, week, month, and year intervals for deadlines, renewal dates, schedules, and planning checks.
How To Use It
- Choose a starting date.
- Enter a whole number and select days, weeks, months, or years.
- Choose add or subtract.
- Review the resulting date, weekday, and date-input format.
Examples
30 days from a date
Add 30 days to a start date to find the future calendar date for a reminder, deadline, or follow-up.
Two weeks before an event
Subtract 2 weeks from an event date to find when preparation should begin.
One month from January 31
Month additions clamp to the final valid day of the destination month.
Useful Notes
Month-end behavior
If the destination month has fewer days, the result uses the last valid day of that month.
Calendar units
Weeks are treated as 7 calendar days. Months and years follow real calendar boundaries instead of fixed day counts.
FAQ
Does January 31 plus one month become February 28?
Yes in a non-leap year. The calculator clamps to the final valid day instead of overflowing into March.
Can I enter decimals?
No. This calculator uses whole day, week, month, or year intervals so the resulting calendar date is unambiguous.
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