Date calculator
Countdown, add days and compare dates
How it works
Compare calendar dates for a countdown, add or subtract days, weeks, months or years, and calculate a date difference. Month arithmetic clamps missing dates to the final day. The default reference date uses your device local date.
Example
October 5 to October 15 is 10 days. Adding one month to January 31 gives the last day of February.
How to use
- Enter your values or choose a local file.
- Choose settings and run the tool.
- Review the result, then copy it or download the file.
Common questions
What rules does this tool use?
Compare calendar dates for a countdown, add or subtract days, weeks, months or years, and calculate a date difference. Month arithmetic clamps missing dates to the final day. The default reference date uses your device local date.
Are my inputs uploaded?
Calculations, texts and files are processed in this browser. The currency tool requests only currency codes from our server.
Free tool · Inputs processed locally · Updated October 5, 2026