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Date Calculator

Count the days, weeks, months and business days between two dates, or add and subtract years, months, weeks and days from a date.

Runs locally, never uploaded

Options

Calculate

Input

Result

Result appears here

What it does

This date calculator answers two everyday questions. How many days are there between two dates? And which date is it a number of days, weeks, months or years from a given date? It is useful for deadlines, project plans, notice periods, subscription terms, ages and countdowns.

For a difference it shows the total days, the same span as years, months and days and as weeks and days, the number of whole months, and how many of the days are business days or weekend days. When adding or subtracting it shows the resulting date with its weekday, day of the year and ISO week number.

How to use

  1. Enter the start date, or click Today. Click Sample to load an example.
  2. Choose what to Calculate: the difference between dates, or add or subtract.
  3. For a difference, type the End date next to the start date; leave it empty to count to today.
  4. To add or subtract, enter years, months, weeks and days in the options, and switch on business days if needed.

Example

From the sample start date to Christmas of the same year:

Start date:  2025-01-01 (Wednesday)
End date:    2025-12-25 (Thursday)
Total days:  358
Years, months, days:  11 months, 24 days
Weeks and days:       51 weeks, 1 day
Business days (Mon–Fri): 256

Adding 10 business days to 2025-01-01 gives 2025-01-15, because the two weekends in between are skipped.

Good to know

All calculations use whole calendar days, so daylight saving changes never shift a result by an hour. A difference is negative when the end date is before the start date. ISO week numbers follow ISO 8601: weeks start on Monday, and week 1 is the week that contains the first Thursday of the year, so the first days of January can belong to the last week of the previous year.

FAQ

› Is the end date included in the count?

Not by default. The difference from Monday to Tuesday is 1 day, as in most calendars and programming languages. Turn on Include the end date when you count both ends, for example the number of days of a trip or a leave from the first to the last day.

› How are business days counted?

Business days are all days except the weekend you choose, Saturday and Sunday by default; Friday and Saturday and Sunday only are also available. Public holidays differ by country and are not removed, so subtract them yourself if they matter.

› What happens when I add one month to January 31?

The day is clamped to the last day of the shorter month, so January 31 plus one month is February 28, or February 29 in a leap year. Years and months are added first, then weeks and days, which is how most date libraries behave.

› Which dates can I use?

Any date from year 1 to year 9999 in the Gregorian calendar, written as YYYY-MM-DD (slashes or dots also work), plus the words today, tomorrow and yesterday. Time of day and time zones are ignored; for those, use the timestamp or time zone converter.