Utilore

Date Calculator

Two questions on one page: how much time lies between two dates, and what date comes out if you move a given number of days forward or back.

— Calendar difference
  • —Days in total
  • —Full weeks
  • —Working days
  • —Weekend days

Days are counted by the calendar, not by hours: twice a year a day is 23 or 25 hours long, and arithmetic on milliseconds loses one whole day.

How to use

  1. Pick the two dates — the counts appear at once.
  2. Tick «count the last day too» if the final day belongs to the period as well.
  3. Switch to «add or subtract» to move a date by years, months or days.
  4. Turn on working days there to skip Saturdays and Sundays.

Good to know

Why days are counted by the calendar

Subtracting one timestamp from another and dividing by 86 400 000 looks right and fails twice a year: on the days clocks change, a day is 23 or 25 hours long. «Exactly 30 days» then comes out as 29 days and 23 hours and rounds down to 29. This calculator works on calendar dates, so the answer holds in every time zone and on every switch.

A month is not thirty days

Add a month to 31 January and the honest answer is 28 February — the last day that exists. A browser left to itself gives 3 March, because it silently overflows into the next month. The same trap catches leap years: 29 February plus one year is 28 February, not 1 March. Both cases are handled here.

Frequently asked questions

Are public holidays taken into account?

No, only Saturdays and Sundays. The set of holidays differs by country and changes every year, and a guessed list would be worse than none: it would look authoritative and be wrong. For an exact count, take the working days from your own calendar.

Why do I get one day less than I expected?

Most likely the last day should count as well. From 1 to 10 January there are nine days of difference but ten days of holiday. That is what the «count the last day too» box is for.

What does «1 year 2 months 3 days» mean exactly?

It is the same distance expressed in calendar units: how many whole years fit, then whole months in the remainder, then days. It is not the total divided by 365 and 30 — those numbers appear separately, as days, weeks and months in total.

Can I calculate an age with it?

Yes: put the date of birth as the first date and today as the second, and the calendar difference is the age in years, months and days. For a birthday, name day or contract date this is the same calculation.

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