What is Date Add/Subtract?

A date add/subtract calculator lets you find a future or past date by adding or subtracting days, weeks, months, or years from any starting date. Use it for deadlines, due dates, expiration dates, or event planning.

The calculator handles four units at once (days, weeks, months, years) and supports negative values via the subtract toggle. Months are calendar-aware: subtracting one month from March 31 lands on the last day of February, not on March 3. The result panel also shows the day of the week and a 'days from today' counter. A second Days Between Dates mode measures the gap between any two dates, breaking it into years, months, and days plus total business days, weekend days, and weeks — with an option to skip US, UK, Canadian, or Australian public holidays.

How to use

1. Select a starting date from the date picker or use today's date as default.
2. Enter the number of days, weeks, months, or years to add or subtract.
3. The result date is calculated instantly, showing the day of the week and how far it is from today.

When to use

• Figuring out a contract end date when the agreement says '90 days from signing'.
• Setting a follow-up reminder six months after a doctor's appointment or vaccine.
• Backing out from a wedding or move-in date to know when to book vendors.

Result

Starting from March 6, 2026: adding 90 days gives June 4, 2026 (a Thursday). Subtracting 6 months gives September 6, 2025 (a Saturday).

FAQ

How does the tool handle months when the start day doesn't exist?

If you add one month to January 31, the result snaps back to February 28 (or 29 in a leap year). The calculator never rolls over into March. Most legal and HR contracts treat month math this same way.

Can I combine all four units in one calculation?

Yes. Enter values for years, months, weeks, and days together and the calculator applies them in that order (years first, then months, then days). Weeks are converted to days internally, so 2 weeks plus 3 days behaves identically to 17 days.

Does it include the start date in the count?

No. 'Add 1 day to March 6' returns March 7, not March 6. If you need an inclusive count (where day one is the start date itself), subtract one from your input.

What about leap years?

The calculator uses the actual Gregorian calendar, so leap days are automatically counted. Adding 365 days to February 1, 2024 returns January 31, 2025 because 2024 has 366 days.

Why does the result show a different day of the week than I expected?

The weekday is computed from the result date, not your starting weekday. Adding 7, 14, or 21 days lands on the same weekday; any other count shifts it. Use this to find the next available Friday or first Monday of next month.

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