Date Calculator
Add/subtract dates & find differences
Date Calculator: Add/subtract dates & find differences. A free, browser-based tool from DevToolbox that runs entirely on your own device: no upload, no account, no tracking.
About the Date Calculator
Free online date calculator. Add or subtract days, weeks, months, and years from any date. Calculate the difference between two dates. Business days support. It is one of the time & date tools on DevToolbox, and like all of them it runs entirely in your browser.
Date handling uses the browser's own Date and Intl support, which means it knows your local time zone and the current daylight-saving rules without asking a server. Unix values are treated as seconds when they are 10 digits and milliseconds when they are 13.
What you can do with it
- Date difference
- Add days to date
- Subtract days
- Business days calculator
- Date math
How to use it
- Enter the date, timestamp or duration you are working with.
- Every equivalent representation is listed at once: ISO 8601, UTC, local time and Unix values.
- Your local time zone is detected from the browser, so local values match your machine.
- Copy the representation you need.
Questions
- Is my data uploaded anywhere?
- No. The tool is JavaScript that runs in the tab you already have open, and DevToolbox has no backend to send anything to. You can open the network tab and watch: after the page and its script load, nothing is sent while you work.
- Does it work offline?
- Once the page has loaded, yes. The tool needs no network access to do its job, so it keeps working if your connection drops. Reloading the page does need the network unless your browser has it cached.
- Is it free, and do I need an account?
- It is free and there is no account, no sign-in and no usage limit. There is nothing to register because there is no server keeping track of anything.
Related tools
The Date Calculator sits in Time & Date, one of the 90 tools on DevToolbox.