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Date Calculator

Choose two dates to count the calendar days and working days between them, or pick a date and add or subtract days, weeks, months, years or working days. Weekends are skipped for working days, and you can list public holidays to skip too. 1 to 31 October 2026 is 30 days, of which 21 are working days.

Runs entirely in your browser

Updated

How to use the Date Calculator

  1. 1Choose Days between dates or Add or subtract.
  2. 2Pick the start date, and the end date or the amount and unit to add.
  3. 3Optionally list public holidays, one YYYY-MM-DD date per line.
  4. 4Read the result; tick Count the start date as well if your rule counts both ends.

How it works

Days between two dates are counted from the day after the start up to and including the end date, so 1 to 2 March is 1 day — the same as subtracting the dates in a spreadsheet. Tick the option to count the start date as well, which is how Excel's NETWORKDAYS counts working days.

Working days are Monday to Friday, minus any holidays you list. Holidays that fall on a weekend are not subtracted twice. Weekend and holiday rules differ between countries and employers, so list the holidays that apply to you.

Adding working days follows Excel's WORKDAY: the start date is not counted, so 1 working day after a Friday is the following Monday. Subtracting works backwards the same way.

Adding months keeps the day of the month where it can. When that day does not exist, the result is the last day of the month: 31 January plus one month is 28 February, or 29 in a leap year. Years work the same way, so 29 February plus a year is 28 February.

Dates are handled as whole days in UTC, so a daylight-saving change can never shift a result by a day. Everything is calculated in your browser.

The formula

days = end date − start date working days = days that are Mon–Fri and not holidays
start date
not counted unless you tick “Count the start date as well”
end date
always counted

Worked example

1 October to 31 October 2026

  1. Calendar days: 31 − 1 = 30
  2. Days counted: 2 to 31 October
  3. Of those 30 days, 9 fall on a Saturday or Sunday, leaving 21 working days

Result: 30 days, 21 working days — or 31 and 22 if the start date is counted too.

Tips and common mistakes

  • Check whether a deadline counts calendar days or working days; contracts and forms often say “business days”.
  • For notice periods, check whether the day notice is given counts — that is the start-date option.
  • List regional holidays before counting working days in December and around Easter.
  • Use ISO dates (YYYY-MM-DD) when sharing deadlines internationally.

Frequently asked questions

Does it include the start and end dates?
By default it counts from the day after the start date up to and including the end date, like subtracting two dates. Tick “Count the start date as well” to include both ends.
How do I count business days excluding holidays?
Open Public holidays to skip and list each holiday as YYYY-MM-DD, one per line. They are left out of working-day counts and skipped when adding working days.
What is 30 days from today?
Choose Add or subtract, keep today's date as the start, enter 30 and choose Days. Choose Working days instead for 30 business days.
Why does adding a month to 31 January give 28 February?
February has no 31st, so the result is the last day of February — the same rule spreadsheets and most date libraries use.
Can I count weeks between two dates?
Yes. The result shows the difference as whole weeks plus days, and as years, months and days.
Are my dates sent anywhere?
No. The calculation runs in your browser.
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