Date Calculator
Count the exact number of days between two dates — instantly, right in your browser.
How to use
- Pick a start date and an end date.
- The day count updates immediately, including a weeks-and-days breakdown.
- Turn on “count both dates” if the first and last day should both be included (for example rental or trip days).
Examples
Days until a deadline
From 2026-08-16 to 2026-12-31 is 137 days — that is 19 weeks and 4 days.
Trip length, counting both days
A trip from 2026-07-10 to 2026-07-19 spans 9 days between the dates, but 10 calendar days when you count both the arrival and departure day.
Counting a contract or notice period
Notice periods and contract terms are usually counted in calendar days, not business days, and whether the first day counts depends on the wording. A term of 30 days from 1 March ends on 30 March if the start day counts and on 31 March if it does not. Because the two readings differ by a day at exactly the moment it matters, set the count explicitly rather than assuming.
Working out a delivery or deadline date
Adding a number of days to a date is safer than counting on a calendar because month lengths and leap years break mental arithmetic. Thirty days from 31 January is 2 March in a common year and 1 March in a leap year — the kind of one-day error that a spreadsheet formula reproduces silently.
Measuring a project span
The gap between a start and an end date is useful in three forms: total days for scheduling, weeks for sprint counting, and approximate months for reporting. Days is the only exact one, which is why it is the figure to use when anything depends on the result.
FAQ
Does the count include the start and end date?
By default the calculator counts the difference between the dates, so from Monday to Wednesday is 2 days. Enable “count both dates” to include both endpoints (Monday to Wednesday becomes 3 days).
Are weekends and holidays counted?
Yes — this tool counts every calendar day, including weekends and public holidays. It does not skip non-working days.
Why is the month value approximate?
Months have different lengths (28–31 days), so a day count cannot be converted into an exact number of months. The tool shows an approximation based on the average month length of 30.44 days and labels it clearly.
What happens if the end date is before the start date?
The calculator still works: it shows the number of days and notes that the end date is earlier than the start date.
Do you handle leap years?
Yes. The calculation uses real calendar dates, so February 29 in leap years is counted correctly.
Why do two date calculators sometimes disagree by one day?
Because of the inclusive-or-exclusive choice at the ends. Counting the days from 1 March to 3 March gives 2 if you count intervals and 3 if you count the days themselves. Neither is wrong; they answer different questions. Check which convention a tool uses before comparing results, especially for anything contractual.
How are months counted when the day does not exist?
Adding one month to 31 January has no exact answer, since February has no 31st. The common convention, used here, is to clamp to the last valid day of the target month, giving 28 or 29 February. That is why adding a month twice and adding two months at once can differ by a day.
Does the calculation handle time zones?
No, and it deliberately does not need to. The tool works on calendar dates rather than timestamps, so there is no hour component to shift across a zone boundary. If your question involves a specific moment rather than a date — a deadline at 23:59 in another country, say — resolve the time zone first and then use the resulting local date here.