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Date Difference Calculator

Count the calendar days, weeks, whole months and weekdays between two dates.

Your Inputs

Turn on to count both the first and the last day, for example a promotion that runs through the end date.

Your Results

Calendar days
84
End date not included
Weeks and days
12 weeks, 0 days
Whole months
2
Complete calendar months
Weekdays
60
Monday to Friday, holidays not excluded

From Mon, Jan 5, 2026 to Mon, Mar 30, 2026.

About the Date Difference Calculator

Writing schedules, pre-order windows, ad campaigns and promotions all depend on counting days correctly. Is that promotion five days or six? How many working days does your editor really have before the deadline? This calculator gives you the answer in several useful forms at once.

Enter a start and end date. You get the number of calendar days, the same span in weeks and days, the number of complete calendar months, and the number of weekdays (Monday to Friday). Tick Include the end date when both the first and last day count, for example a price promotion that runs from Monday through Friday inclusive.

If you are planning a book, the Book Deadline Calculator turns days into a daily word target, and the Publishing Countdown Calculator back-plans launch milestones from your release date.

How It Works

Dates are compared as whole calendar days, so time zones and daylight saving changes do not affect the count.

By default the count excludes the end date, the same way "days until" is usually counted. Including the end date adds one day.

Weekdays count Monday to Friday only. Public holidays are not removed, because they differ by country.

If the end date is before the start date, the tool counts the gap and tells you it runs backwards.

Formula

Days
Days = End date − Start date (+1 if the end date is included)
Weeks
Weeks = floor(Days ÷ 7), remainder in days

Example

An editing window from 5 January to 30 March 2026

  1. Start date: Monday 5 January 2026. End date: Monday 30 March 2026.
  2. Calendar days: 84, which is exactly 12 weeks.
  3. Whole months: 2 (5 January to 5 March, with the rest of March not a full month).
  4. Weekdays: 60 working days for your editor.
  5. With the end date included: 85 days and 61 weekdays.

The window is 84 days, or 60 weekdays, before you decide whether the final day counts.

Important Notes

  • Weekday counts do not remove public holidays or personal time off.
  • Whole months count complete calendar months only. A span from 31 January to 28 February is 0 whole months.
  • Dates use the Gregorian calendar and the format your browser shows in the date picker.
  • Nothing is stored. Dates stay in your browser.

Frequently Asked Questions

Should I include the end date?

Include it when both the first and last day are active days, such as a promotion running Monday to Friday (5 days). Leave it off for "how many days until" questions, such as days until a release date.

Why does the weekday count look low?

Weekdays exclude Saturdays and Sundays. Over 12 weeks that removes 24 days. Holidays are not removed, so your real working days may be fewer still.

How are months counted?

Only complete calendar months are counted, from the start day of the month to the same day in a later month. Partial months appear in the day count instead.

Can I count backwards?

Yes. If the end date is earlier than the start date, the tool shows the size of the gap and notes that it runs backwards.

How do I check a KDP Select enrolment period?

KDP Select enrolment runs in fixed terms. Enter the start and end dates shown in your KDP Bookshelf to see exactly how many days remain.

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