Date Add/Subtract Calculator

Move a date forward or backward

Choose a starting date, then enter positive amounts to add or negative amounts to subtract. Years and months are applied first, followed by weeks and days.

Calendar arithmetic, not hour arithmetic

This calculator works with calendar dates. One week is seven calendar days. A month means moving to the corresponding month, not adding 30 days, and a year means moving to the corresponding year, not adding 365 days. That distinction matters around short months and leap years.

What happens at the end of a month

When the destination month lacks the starting day number, the result uses that month's final valid day. Adding one month to January 31 produces February 28 in a common year or February 29 in a leap year. The calculator then applies any week or day adjustment to that clamped date.

Worked example

Start with January 31, 2027. Add one month and seven days. The month step lands on February 28 because February has no 31st. Adding seven more days produces March 7, 2027. Entering −1 month and −7 days instead moves backward in the same ordered stages; it is not guaranteed to reverse every clamped end-of-month result.

Order can change the answer

Adding one month and then one day can differ from adding one day and then one month. This page always uses years, months, weeks, then days so results stay consistent. If a contract, subscription, or billing system documents another rule, follow that system's definition.

Useful planning cases

Date offsets help with maintenance reminders, project checkpoints, warranty periods, recurring reviews, planting schedules, and personal milestones. They do not automatically exclude weekends or holidays. Use the Business Day Calculator when only weekdays should count.

Assumptions and limitations

All amounts must be whole numbers. Dates are calculated in the browser's local calendar without a time of day, so daylight-saving transitions do not add or remove an hour from the result. The page does not interpret time zones, business hours, legal deadline rules, fiscal calendars, or historical calendar changes. Very large offsets may exceed the browser's supported date range.

Date Add/Subtract FAQ

Can I subtract a date amount?

Yes. Use a negative number in any field.

Is one month always 30 days?

No. The calculator moves by calendar month and respects each month's actual length.

Does the starting date count as day one?

The start is day zero. Adding one day returns the next calendar date.