Add or subtract days
Move a date forward or backward by any number of days — due dates, reminders, look-backs.
How adding and subtracting days works
Enter a start date, type how many days to move, choose “Add days” or “Subtract days”, and the calculator lands on the resulting date — telling you its weekday too. Perfect for “90 days from today” payment terms, travel returns, or counting back from a deadline.
Month and year boundaries are handled automatically: January 30 plus 5 days is February 4, and leap years are respected, so adding days across February 29 works correctly.
result = start date ± N × 24 hours
Add or subtract days FAQ
What happens at month or year boundaries?
They roll over automatically. January 30 plus 5 days gives February 4, and December 30 plus 5 days gives January 4 of the next year.
Are leap years handled?
Yes. February 29 exists in leap years, so date math crossing it stays exact.
Can I enter a negative number of days?
Use the “Subtract days” button instead — the day count itself must be zero or positive.
Is there a limit on the number of days?
No practical limit. Very large counts still compute instantly.