Date Add/Subtract Calculator
A free, browser-based calculator. Runs entirely in your browser — no sign up, nothing stored.
100% FreeRuns in your browserBasic
Enter details
Result
Enter the details to see your result.
Runs in your browser. Your inputs are not saved or transmitted.
How to use this calculator
- Choose a start date.
- Pick add or subtract and enter years/months/weeks/days.
- Read the resulting date and weekday.
How it works
Years and months are applied first (clamping to the end of shorter months), then weeks and days are added as exact day counts.
Worked example
31 Jan 2026 + 1 month. = 28 Feb 2026 (clamped to the last day of February).
Tips
- Runs entirely in your browser. Your inputs are not saved or transmitted.
Frequently asked questions
Why did adding a month not give the 31st?
Shorter months are clamped to their last day, so 31 Jan + 1 month = 28 Feb.
Privacy?
Runs entirely in your browser. Your inputs are not saved or transmitted.
Related tools
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.