Quick answer: The date calculator counts the days between two dates, or adds and subtracts years, months, weeks and days from a date. From 1 January 2026 to 31 December 2026 there are 364 days, of which 260 are weekdays. Adding one month to 31 January lands on the last day of February, because February has no 31st.
Deadlines, notice periods, project plans, warranties and countdowns all come down to the same question: how many days from here to there, or what date is it when I add this much time? This calculator answers both.
The first tab counts the days between two dates and breaks the gap into weeks, months and weekdays. The second tab starts from a date and adds or subtracts any mix of years, months, weeks and days.
How the dates are worked out
Days between dates are counted in whole calendar days. By default the start date is counted and the end date is not, so January 1 to January 2 is 1 day. Tick “include the end date” to count both ends, which is common for bookings and inclusive periods.
Weekdays are Monday to Friday. Public holidays are not excluded because they differ by country and region, so subtract them yourself for a business-day count.
When you add months, the day of the month stays the same where possible. If it does not exist in the target month, the calculator uses the last day of that month, so January 31 plus one month is February 28 (29 in a leap year). Years and months are added first, then weeks and days.
A worked example
Example. From January 1, 2026 to December 31, 2026 is 364 days (365 if you include the last day). Of the 364 days, 260 are weekdays. Adding 90 days to January 1, 2026 gives Wednesday, April 1, 2026.
Days between some dates
| From | To | Days between |
|---|---|---|
| 1 January 2026 | 1 March 2026 | 59 |
| 1 January 2026 | 1 July 2026 | 181 |
| 1 January 2026 | 31 December 2026 | 364 |
| 1 January 2028 | 1 March 2028 | 60 |
| 19 September 2026 | 31 December 2026 | 103 |
The end date is not counted, so 1 January to 2 January is 1 day. In a leap year such as 2028, February has 29 days, which adds one day to any span that includes it.
Common mistakes to avoid
- Deciding whether to count the start day. The difference between two dates leaves out one end, so include it yourself if you want both days counted.
- Assuming a month is 30 days. Months have 28 to 31 days, and adding “one month” follows the calendar.
- Treating weekdays as working days. Public holidays are not excluded, so subtract them yourself for a working-day count.
Frequently asked questions
How many days are there between two dates?
Choose both dates on the first tab. The main figure is the number of days between them, not counting the end date unless you tick the option to include it.
Does it count weekends and holidays?
The total counts every day. The weekdays and weekend days figures split it up. Public holidays are not removed, since they vary by place.
What is 90 days from today?
Open the second tab, keep the start date as today, leave Days at 90 and choose Add. The result shows the date and the day of the week.
Can I count backwards from a date?
Yes. Choose Subtract on the second tab, or enter an end date earlier than the start date on the first tab. Both work.
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Sources and further reading
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