Date Calculator
Add or subtract days, weeks, months, or years from a date with correct month-end handling.
Result
Complete the fields to see the result.
The calculation runs locally in your browser.
How to add or subtract time from a date
Choose a start date, operation, and a number of days, weeks, months, or years. Civil-date arithmetic avoids daylight-saving shifts.
For example, adding 6 weeks advances exactly 42 calendar days.
Month ends and leap years
When the original day does not exist in the destination month, the result uses that month's last valid day. January 31 plus one month becomes February 28 or 29.
Frequently asked questions
How do I calculate a future date?
Choose Add, enter an amount, and select days, weeks, months, or years.
Can I calculate a past date?
Yes. Choose Subtract to move backward from the start date.
What happens when adding one month to January 31?
The result is clamped to February's last valid day.