Date +/- Weeks Calculator

Yes. This calculator supports up to 5,200 weeks (100 years), so you can calculate dates for long-term planning, warranty periods, lease terms, or any multi-year interval expressed in weeks.

Yes. Since the calculation is based on adding or subtracting actual days (weeks x 7), it automatically handles leap years. If the interval spans February 29 of a leap year, that day is counted normally.

This calculator focuses on weeks only. For combined week-and-day calculations, use the Date +/- Days Calculator separately. You can chain the results: first add weeks, then use that result date to add or subtract the remaining days.

The result date itself is not affected by DST, since the calculation is purely calendar-based (adding whole days). Time-of-day calculations would be affected by DST, but this tool only works with dates, not times.

The day of the week is shown because it often determines the practical usefulness of a date. Deadlines, appointments, and events usually need to fall on a specific type of day (weekday vs. weekend). Knowing the day instantly lets you decide whether to adjust the date.

To find the number of weeks between two dates, use a Date Difference Calculator or divide the number of days between the dates by 7. This calculator works in the opposite direction — it finds a date given a starting point and a number of weeks.

Yes. For example, if your last menstrual period (LMP) was a specific date, you can add 40 weeks to estimate your due date. However, for medical planning, always confirm with a healthcare provider, as due dates are estimates.

The calculator correctly rolls over into the next year. For example, adding 4 weeks to December 20, 2026 yields January 17, 2027. JavaScript Date arithmetic handles year boundaries automatically.

No — the start date itself is day 0. Adding 1 week moves to 7 days after the start date. For example, adding 1 week to Monday March 9 gives Monday March 16. This follows the standard convention for date arithmetic.