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Choose what your account keeps in step on every device where you are signed in.

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    Always synced: the tools on your board, their order and size.

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Turning something off removes it from your account straight away. Your devices keep their own copy.

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Your choice is stored in this browser only. Notifications never show personal content such as a message or a number. They work while a Synsi tab is open; closed tabs get none.

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Date Add or Subtract Calculator

Add or subtract a number of days, weeks, months or years from a date, with month-end dates handled safely.

My tools →

Result date

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Day of the week

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Calendar days moved

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Date and time results follow the Gregorian calendar and standard time-zone data. Working-day counts exclude weekends but do not automatically remove public holidays. Check local rules and daylight-saving transitions when timing is critical.

Runs in your browser – your data never leaves your device Also available via our free API

How to use the Date Add or Subtract Calculator

  1. 1 Enter the date, time or values you want to calculate.
  2. 2 Review the result and the assumptions shown with the calculator.

How this calculator works

Calendar months and years preserve the day of the month when possible and clamp to the last valid day otherwise. Days and weeks move by their exact calendar-day count.

Assumptions and limitations

The result follows the Gregorian calendar. Adding one month to a date near the end of a month may land on the final day of the next month.

Frequently asked questions

How is the result calculated?

Calendar months and years preserve the day of the month when possible and clamp to the last valid day otherwise. Days and weeks move by their exact calendar-day count.

What should I keep in mind?

The result follows the Gregorian calendar. Adding one month to a date near the end of a month may land on the final day of the next month.

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