HandyjarFind a tool

Calculators

Add & subtract days

Find a date before or after your starting date.

Start with a date

Add or subtract days, weeks, months or years.

Year-month-day, for example 2024-01-31.

Use a whole number. Negative amounts reverse the direction.

Loading the calculator…

Result

Enter your starting date and amount, then select Calculate date.

How to use

  1. Enter your details

    Set a start date, direction, amount and calendar unit.

  2. Calculate

    Select Calculate date. Changing any input clears the previous result.

  3. Use your result

    Copy the ISO date or download a text report with the calculation and rules.

Calendar rules

  • Calendar days include weekends. Holidays count too. One day after January 1 is January 2; zero leaves the date unchanged.
  • Weeks are seven days. Date-only UTC arithmetic keeps local time zones and daylight saving from shifting the result.
  • Months and years go directly to the target month. Keep the day when possible, otherwise use that month’s last day. January 31, 2024 + 1 month = February 29; + 2 months = March 31.
  • Negative amounts reverse the direction. Subtracting −3 days adds 3 days.

Frequently asked questions

What happens with leap days and month ends?

February 29, 2024 + 1 year becomes February 28, 2025. The result and report disclose this adjustment. Clamping is not always reversible: subtracting one month from February 29 gives January 29, not January 31.

Which dates can I enter?

Use YYYY-MM-DD or a signed six-digit year such as +010000-01-01. The native browser Date range is −271821-04-20 through +275760-09-13. Year 0000 means 1 BC. Dates use the proleptic Gregorian calendar, even before its historical introduction. Amounts must be exactly representable whole numbers; dates outside the native range produce an error.

Does this calculate business days or exact elapsed hours?

No. It counts calendar dates, including all weekends and holidays. A local day around a daylight-saving change can have 23 or 25 hours; this calculator does not compute elapsed hours.

Are my inputs saved?

Inputs and results stay in this tab and are not uploaded or saved in browser storage. Copy and download only happen when you select those actions. Your downloaded report contains the entered calculation.

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Calculated in your browser.
Your dates and calculations are not sent to a server.