Date Difference Calculator
Count exactly how many days are between two dates. Enter a start and end date to get the number of days, weeks, months and years between them, plus a year/month/day breakdown.
How it works
The calculator measures the elapsed whole days between the two calendar dates, then converts that total into weeks, average months and average years for convenience. Ticking “Include both start and end dates” also counts the first and last day — for leave days, hotel stays and event durations.
Difference = (End date) − (Start date)Worked examples
1 January 2024 to 31 January 2024
30 days. The start date is not counted, so the answer is the elapsed days between the two dates.
1 January 2020 to 1 January 2024
1,461 days: four years, including the leap day 29 February 2020.
Entering one date as both start and end
Entering 1 January 2026 as both the start and the end gives 0 days, 0 weeks and 0 months. With the option to include both dates ticked it gives 1 day, which is the difference between elapsed time and the number of calendar days touched.
What this assumes, and where it does not apply
What it assumes
- Counts elapsed days between the two dates, excluding the start date.
- Both dates are read as calendar dates with no time of day, so no time-zone conversion applies.
- The result is counted in whole days, so any time of day attached to either date is ignored and the two dates are compared as calendar dates.
Where the result does not apply
- Public holidays and working days are not considered: a notice period that runs in working days will differ.
- A contract or tenancy that counts a period inclusively of both end dates will be one day longer than the figure here.
- A tenancy or contract that runs in whole calendar months will not match the months figure here, which is built from an average month length rather than from the calendar.
Frequently asked questions
How many days are between two dates?
The calculator measures elapsed time between the two dates. For example, January 1 to January 31 is 30 days.
How do I count leave days or a hotel stay including both dates?
Tick “Include both start and end dates” to count the first and last day too — for example, 1 January to 31 January becomes 31 days. Leave it off for elapsed days between dates.
How many weeks are in a year?
There are 52 weeks and 1 day in a common year, or 52 weeks and 2 days in a leap year.
Why are months and years approximations?
Months and years vary in length, so the calculator uses average values (30.4375 days per month, 365.25 days per year).
Why is 1 January to 2 January one day and not two?
Because the answer is the elapsed time between the two dates. From the start of 1 January to the start of 2 January is one day; tick the option to include both dates to count the calendar days themselves and get two.
Maintained by David M at Delta Tech Solutions · Figures last checked 10 October 2026 · Next check due 10 April 2027
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