Date Calculator
How many days until the deadline? What date is 90 days from today? Count, add and subtract dates — including working days.
- Days between dates
- Working days
- Add or subtract
- Private
How to calculate with dates
Three modes for three kinds of question.
- 1
Choose a mode
“Days between dates”, “Add or subtract” or “About a date”.
- 2
Enter the dates
Pick a start and an end date, or a start date and the time to add or subtract.
- 3
Read the result
Get the days, weeks, months and working days — or the resulting date with its weekday and week number.
Every date question in one place
Deadlines, notice periods, trips and countdowns.
Days between dates
The span in days, in weeks and days, and in years, months and days.
Working days
Count Monday to Friday only — or choose a different weekend for your country or job.
Add and subtract
Add any mix of years, months, weeks and days to a date, or subtract it.
Deadlines in working days
Find the date that is, say, 10 working days from today.
About a date
Weekday, ISO week number, day of the year, days left in the year, quarter and leap year.
Link to your calculation
Copy a link that reopens the calculator with your numbers filled in — handy for sharing or saving a scenario.
Made for phones
Large fields, the right keyboard for numbers and a layout that fits small screens.
Private by design
Everything is calculated in your browser. Your numbers are not sent to a server.
Counting days correctly
The number of days between two dates is the difference of the dates: from 1 March to 31 March is 30 days, because the start day is not counted. If both the first and the last day count — a hotel stay billed per day, a rental, an event — switch on “Count the end date too” to get 31. This off-by-one is the most common mistake in date arithmetic.
Months are not a fixed length, so adding a month means moving to the same day of the next month. When that day does not exist, the last day of the month is used: 31 January plus one month is 28 February (29 in a leap year). Adding 30 days is something different and lands on 2 March.
Working days skip the weekend, by default Saturday and Sunday. Public holidays differ by country, region and even employer, so they are not removed automatically — subtract the ones that apply to you. For week numbers the calculator uses ISO 8601: weeks start on Monday and week 1 is the week containing the first Thursday of the year.
Common time spans in days
| Span | Days | Note |
|---|---|---|
| 1 week | 7 | |
| 30-day notice | 30 | Not the same as one month |
| Quarter | 90–92 | Depends on the months |
| Half a year | 181–184 | |
| Year | 365 or 366 | Leap year every 4 years, except century years not divisible by 400 |
Tips
- For an exact age or the next birthday, use the Age Calculator.
- Adding up hours and minutes instead of days? Try the Time Calculator.
- Track working hours across a week with the Hours Calculator.
- Legal and contractual deadlines often have special counting rules (first day excluded, extension to the next working day). Check the rule that applies before relying on a date.
Frequently asked questions
Can’t find your answer? Contact us — we reply quickly.
How do I count the days between two dates?
Subtract the start date from the end date. The start day is not counted; switch on “Count the end date too” if both days should count.
How are working days counted?
Every day from the start date up to, but not including, the end date is checked; days that fall on the selected weekend are skipped. Public holidays are not excluded.
What date is 90 days from today?
Choose “Add or subtract”, keep today as the start date and enter 90 days. The result shows the date, its weekday and the week number.
What happens when I add a month to the 31st?
If the target month has no such day, the last day of that month is used: 31 January + 1 month = 28 or 29 February.
Which week number system is used?
ISO 8601, the standard in Europe: weeks run Monday to Sunday and week 1 contains the first Thursday of the year. US-style week numbering can differ by one.
Are my numbers stored or sent anywhere?
No. The calculation runs in your browser. Your last inputs are remembered on your own device only, so the form is still filled in when you come back; use Reset to clear them.
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