This date calculator adds or subtracts days, weeks, months, or years from a starting date to find the resulting date.
Everyday life
Date Calculator
Find the difference between two dates or add and subtract time from a date.
Calculator
About this calculator
Formula notes
Month and year shifts follow calendar rules (clamping at month end); day and week shifts count fixed 24-hour periods.
Worked examples
- Example: 2026-01-31 plus one month clamps to 2026-02-28, since February has no 31st.
- Adding 30 days to 2026-01-31 gives 2026-03-02; adding one calendar month would be a different operation with a different result.
How to use it
- Pick the start date.
- Choose add or subtract and the amount.
- Read the resulting date and weekday.
Frequently asked questions
Why does Jan 31 + 1 month not give Mar 3?
The calculator clamps to the target month's last valid day instead of overflowing.
Are months 30 days here?
No. Month arithmetic uses real calendar months of 28–31 days.
Limits and interpretation
- A fixed number of days is not equivalent to a calendar month or year.
- The calculator uses calendar dates and does not incorporate time zones, times of day, or daylight-saving transitions.