Date Difference Calculator
Count the days, weeks and months between two dates.
Count the time between two dates. Enter a start and end date to see the number of days, weeks and approximate months and years in between.
Formula / method
Examples
365 days
59 days
Counting the gap between dates
Give the tool a start date and an end date and it returns the span between them expressed in days, weeks and months. It counts the actual calendar days, so it automatically accounts for months of different lengths and for leap years, where February has 29 days.
Weeks are simply the day count divided by seven, and months are approximate because calendar months vary from 28 to 31 days. For exact billing or contract periods, the raw day count is the most reliable figure to rely on.
Inclusive versus exclusive days
A common source of confusion is whether both endpoints are counted. From the 1st to the 10th there are nine days between the dates, but ten days if you include both the first and last day. Decide which meaning you need, for example when counting hotel nights (exclusive) versus event days (inclusive).
To count down to an upcoming deadline instead of measuring a past gap, try the Days Until Date tool.
Where it's used
- Counting the days left on a visa, passport, or contract before it expires
- Working out the number of nights for a hotel or Airbnb booking
- Measuring the length of a billing or project period between two invoice dates
- Counting notice periods and payment-due windows in HR and legal paperwork
- Figuring out how many days until or since a wedding, birth, or anniversary
Real-world examples
- A lease running 2025-03-15 to 2026-03-14 shows 364 days, confirming a one-year term counted by nights.
- A stay booked from Aug 3 to Aug 10 returns 7 days, matching the 7 nights you are charged for.
- A freelancer billing for work between Jan 1 and Feb 15 counts 45 days to charge against a daily rate.
Did you know?
The Gregorian calendar skips a leap day on century years that are not divisible by 400, so the average year is 365.2425 days long. That rule is why 1900 was an ordinary year but 2000 was a leap year.
FAQ
Are the start and end days both counted?
This counts the number of nights between the two dates. Add one if you need to include both the first and last day.