Date Add or Subtract Calculator
Add or subtract days, weeks, months or years from a calendar date.
Result
Resulting date: February 28, 2026
Adding months or years preserves the day when possible and otherwise uses the last valid day of the target month.
- Day of week
- Saturday
- Actual day change
- 28
https://calcgallery.com/date-time/date-add-subtract-calculator/
Calendar results use the proleptic Gregorian calendar. Timezone results use the IANA data supplied by your browser or server, whose political rules can change. Confirm critical schedules with the people or service involved. Read the full disclaimer
How to use the Date Add or Subtract Calculator
- Enter the starting date.
- Choose Add or Subtract, enter an amount and select the calendar unit.
- Check the resulting weekday and actual change in days.
A visible end-of-month rule
Days and weeks move by fixed day counts. Months and years are calendar operations: they preserve the day number when possible and use the final valid day otherwise. That makes cases such as January 31 plus one month deterministic instead of depending on browser overflow behavior.
The actual day change helps show the consequence. One month can move 28, 29, 30 or 31 days.
With your numbers
- Add 1 months from 2026-01-31
- Result = 2026-02-28; actual calendar-day change = 28
Quick reference
Adding months or years preserves the day when possible and otherwise uses the last valid day of the target month.
| Example | Resulting date |
|---|---|
| One month after January 31 | February 28, 2026 |
| Thirty days later | October 20, 2026 |
| One year after leap day | February 28, 2025 |
| Two weeks earlier | September 6, 2026 |
| No change | September 20, 2026 |
| Four hundred years later | February 29, 2400 |
Common questions about the Date Add or Subtract Calculator
- What is one month after January 31?
- The result clamps to the last valid day of February. The same rule applies whenever the target month lacks the starting day.
- Is adding one year always 365 days?
- No. Leap years make some year-long calendar steps 366 days, which is why the actual day change is shown separately.
- Does adding weeks depend on the locale?
- No. One week is exactly seven calendar days regardless of which weekday a locale treats as the first day.