Date Calculator: Add or Subtract Time
Add or subtract a period from a starting date. Combine years, months, weeks, and days, then repeat the same interval to generate a series of dates.
Date arithmetic and month ends
Calendar months have different lengths. If the original day number does not exist in the target month, the calculator uses that month’s last day. Repeated intervals are applied successively, which is useful for recurring review dates, billing reminders, or project milestones.
Frequently asked questions
Can I add or subtract months?
Yes. Choose Add or Subtract and enter any combination of years, months, weeks, and days.
What happens when the target month is shorter?
The result uses the last valid day of the target month. For example, adding one month to January 31 lands on the final day of February.
Can I repeat a date calculation?
Yes. Set the repeat count to create a sequence using the same interval from each result date.
Does the calculation run in my browser?
Yes. Dates are calculated on your device and are not sent to a server.