Add or subtract dates
Find a date by adding or subtracting years, months, weeks, and days.
Your inputs
Choose your dates and the calculation convention. Results update as you edit.
Calculations run in your browser. Inputs are not saved or sent to analytics.
How it works
- Resulting date = + → → (7 × + )
- Worked example: Add one month to 2026-01-31 with no other changes. February has no 31st, so the result is clamped to its last day. Adding a month does not always mean adding 30 days.
- 2026-01-31 → 2026-02-28.
Input and formula key
Your result
Complete the inputs to see your result.
Assumptions and limitations
Apply years, then months, then weeks/days. If the destination month lacks the original day, use its last day.
Sources
- US Naval Observatory — Calendars and conversion algorithms Sources reviewed: 2026-10-05
