About DateUtils
What DateUtils is
DateUtils is a collection of 20 free date and time tools: calculators for the gap between dates, working days and ages, converters for formats, day numbers, Unix timestamps and time zones, and calendar references such as ISO week numbers and leap years.
Why it exists
Date arithmetic looks trivial and is full of small decisions: whether the first day counts, what one month after 31 January means, how a clock change affects a countdown. Many calculators make those decisions silently. DateUtils makes them visible, documents them on each page and tests them, so you can tell whether a result answers the question you meant to ask.
Accuracy
- Calendar arithmetic uses the Gregorian calendar with exact integer maths, independent of your device's time zone.
- Time zone conversion uses the IANA time zone database through your browser, not fixed offsets, so daylight saving changes and unusual offsets are handled from real rules.
- The calculation code is covered by automated tests that include leap years, month ends, year boundaries, ISO week edge cases, dates before 1970 and after 2038, and daylight saving transitions.
- Where a calculation has limits or more than one accepted convention, the page says so.
Privacy
Every calculation runs in your browser. There are no accounts and no forms that send what you enter to a server. Analytics and advertising, when they are switched on, load only after you agree and never receive the values you type. See the privacy policy for details.
Independence and limits
DateUtils is an independent website. It does not provide legal, financial, medical or other professional advice, and its results are not certified for any official purpose. For contracts, deadlines set by law, payroll or immigration matters, check the rules that apply to you. See the terms of use.
Feedback
If a result looks wrong or a tool is missing something, please get in touch. Corrections to calculations are treated as bugs and each one gets a regression test.