Date Calculator
Free online date calculator: add or subtract years, months, weeks, days and more, or diff two dates precisely.
Privacy: all processing happens locally in your browser. Your input never leaves your device.
What is Date Calculator?
Questions like "what date is 30 days from now" or "how many days between two releases" are easy to get wrong in your head because of month lengths and leap years. This tool adds or subtracts years, months, weeks, days, hours, minutes and seconds from any base date, and computes the precise difference between two dates (days + hours + minutes + seconds), handling leap years and month lengths automatically.
How to Use
- Pick a base date or two dates
- Enter the amount and unit to add/subtract (or view the difference)
- Copy the result
FAQ
- What is January 31 plus one month?
- By JavaScript semantics it is March 3 (February has no 31st, so it rolls over). For billing cycles, agree on a business rule separately.
- Is the difference counted in calendar days or 24-hour units?
- It is computed as an exact 24-hour-based difference, then displayed as days + hours + minutes + seconds.
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Last updated 2026-09-04