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Duration Calculator

Add or subtract time from a date, or convert between duration units.

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Input

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Settings

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Run

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Results

Results will appear here once you run the tool.

About Duration Calculator

Add or subtract time from a date, or convert between duration units. Duration Calculator needs no input file — choose your settings and it generates the result straight away.

Your files stay on your device. ZyncTools has no upload step: the file is read in your browser, processed there, and handed straight back to you. There is no account, no watermark and no size cap beyond what your own device can hold.

Settings. Duration Calculator gives you control over mode, starting date, starting time, operation, years, months, weeks and days, plus 5 more.

Also known as: duration, add days, subtract, deadline, convert time.

How to use Duration Calculator

  1. Open the tool. Open Duration Calculator. There is nothing to upload — it works from the settings alone.
  2. Choose your settings. Adjust mode, starting date, starting time and the other 10 settings to suit what you need.
  3. Generate. Press Generate. The result appears immediately and updates whenever you change a setting.
  4. Save the result. Copy the output, or press Download to save it. Nothing is kept once you close the tab.

Frequently asked questions

Are my files uploaded when I use Duration Calculator?

No. Duration Calculator runs entirely inside your browser. Your file is read locally, processed on your own device, and handed straight back to you. You can confirm this yourself: open your browser's developer tools, watch the Network tab, and run the tool — no request carries your data anywhere.

Is Duration Calculator free?

Yes, completely. No account, no sign-up, no watermark on your output, and no cap on how many times you can use it. The project is open source under the AGPL licence.

Does Duration Calculator work offline?

Mostly. The site caches itself after your first visit, so it keeps working without a connection. Tools that need a specialised library — PDF editing, OCR, QR codes, MP3 encoding — need a connection the first time you run them, then that library is cached too.

Related date & time tools

Unix Timestamp Converter Convert Unix timestamps to readable dates and back, in any time zone. Date Difference Calculator Work out the time between two dates, with or without weekends. Age Calculator Calculate exact age in years, months, days — and the next birthday. Time Zone Converter See what one moment in time looks like across several time zones. Cron Expression Parser Explain what a cron expression means and when it will next run. Countdown Timer Count down to a date and see exactly how long is left.