Date Add/Subtract Calculator
Add or subtract days, weeks, months, or years from any date. Find future or past dates instantly with this simple date math tool.
Runs in your browser. No data leaves your device.
Frequently Asked Questions
How does the Date Calculator work?
The tool creates a JavaScript Date object from the start date, then calls the native setDate, setMonth, or setFullYear mutator methods to add or subtract the specified amount. For weeks, it multiplies by 7 and uses setDate. JavaScript's Date object automatically handles month-end overflow (e.g. January 31 + 1 month rolls to the last day of February) and leap year boundaries through internal calendar normalization.
Can I add and subtract multiple units at once?
Yes. You can combine years, months, weeks, and days in a single calculation. For example, add 1 year and 3 months from today to find a future date.
How does it handle months with different lengths?
Adding one month always moves to the same day of the next month. If that day does not exist (e.g., adding one month to January 31), it rolls to the last day of the target month.
Can I calculate a date in the past?
Yes. Switch to subtract mode and enter the number of days, weeks, months, or years to go backwards from any starting date.