Add or subtract days, weeks, months, or years from any date, with business day support.
Date arithmetic on the proleptic Gregorian calendar starting from 2026-09-04 (Friday). Useful for deadlines, project timelines, and recurring events.
| Start | Add/subtract | Result | Day of week |
|---|---|---|---|
| 2026-09-04 | + 30 days | 2026-10-04 | Sunday |
| 2026-09-04 | + 90 days | 2026-12-03 | Thursday |
| 2026-09-04 | + 1 year | 2027-09-04 | Saturday |
| 2026-09-04 | + 6 months | 2027-03-04 | Thursday |
| 2026-09-04 | − 7 days | 2026-08-28 | Friday |
| 2026-09-04 | + 12 weeks | 2026-11-27 | Friday |
Adding 1 calendar year to a date preserves month and day-of-month; adding 6 months preserves day-of-month unless the target month is shorter (clamped to last day).
Adding years keeps the same month and day. Leap year Feb 29 becomes Feb 28 in non-leap years.
Months have different lengths (28-31 days). Our calculator handles overflow correctly.
Simple addition or subtraction of calendar days, accounting for month boundaries.
Cross-checked against authoritative formulas (IRS, NIST, ACSM) and updated for 2025/2026 tax years and rates.
No server roundtrip. All math runs in your browser so results appear the moment you finish typing.
We never collect, store, or transmit your inputs. Every calculation runs locally in your browser.
Each calculator includes the formula, plain-English explanation, and FAQs so you understand the result.
Estimates only. Calculator results are for educational and planning purposes — not professional advice. For binding decisions on taxes, investments, health, or legal matters, consult a qualified professional.
FAQ
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A date add and subtract calculator is a free tool that finds a future or past date by adding or subtracting days, weeks, months, or years from a starting date. Our date add and subtract calculator handles leap years, varying month lengths, and business day mode. The calculator is used for deadlines, project planning, and recurring events.
How it works
Calculate a future or past date by adding or subtracting days, weeks, months, or years, in three steps.
Select the starting date using the date input. The calculator defaults to today. You can pick any past or future date within the supported range.
Use the Days input for calendar days, or switch to Weeks, Months, or Years for larger units. Enter a negative number to subtract. Toggle Business days to skip weekends automatically.
The result shows the target date, the day of the week, and the total calendar/business days between the two dates. The share button creates a link with your inputs pre-filled, useful for sharing deadlines or event dates.
Add or subtract days, weeks, months, or years from any date.
Find the exact number of days between two dates, including business days.
Find the exact age in years, months, and days from a birth date.
Count days between two dates with optional business-day mode that skips weekends.