Date Calculator
Add or subtract days, weeks, months, or years from a start date.
Inputs
Result
Enter values on the left and select Equals to see the result here.
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What the Date Calculator does
- Finds the date after adding or subtracting a specified amount of time.
- Shows the resulting date and day of week.
How to use the Date Calculator
- Choose a start date.
- Enter an amount and select unit (days/weeks/months/years).
- Choose add or subtract, then click Calculate.
Formula / methodology used
- Uses calendar-aware date math (months/years roll correctly).
- Outputs ISO date format (YYYY-MM-DD) for international clarity.
Example calculation
Add 6 weeks to 2026-03-17.
- Start = 2026-03-17
- Unit = weeks, amount = 6
- Add 42 days
Result: Outputs the resulting date and weekday.
Date Calculator FAQs
Why does adding months sometimes change the day number?
Some months have fewer days. The browser’s date handling adjusts accordingly.