How the date difference calculator works
Pick a start date and an end date and the calculator counts the days between them, then expresses the same gap in several ways: years, months and days; months and days; weeks and days; working weekdays (Monday to Friday); hours; and years as a decimal. It handles leap years and months of different lengths automatically. If the end date comes before the start date, it still measures the gap and tells you the dates are reversed.
How the difference is counted
Days = end date − start date (add 1 if the end date is included)
By default the count excludes the end date, the same way you would count nights in a hotel stay: from 1 January to 2 January is one day. Choose "Yes, add 1 day" when both the first and last day should count, for example when working out leave days, the length of an event or a notice period that includes the final day.
For the years, months and days figure, the calculator counts whole calendar months first and then the remaining days, so 31 January to 1 March in a leap year is 1 month and 1 day (30 days in total).
Worked example
From 1 January 2026 to 31 December 2026:
- Total: 364 days, which is exactly 52 weeks
- In calendar terms: 11 months and 30 days
- Weekdays (Mon–Fri): 260
- Including the end date: 365 days, the full year
Useful ways to use it
- Notice periods and contracts: check the exact number of days to a last working day.
- Loans and deposits: count the days for interest calculations that use a daily rate.
- Project planning: the weekday count gives a quick estimate of working days (public holidays are not removed, so subtract them yourself).
- Countdowns: click "Today" for the start date and pick a wedding, exam or trip date as the end date.
- Pregnancy and health tracking: count weeks and days from a given date.
Use Share to send a link with both dates filled in, or Copy to paste the full breakdown into a message or document.
Frequently asked questions
How do I count the days between two dates?
Enter the start and end dates above. The calculator subtracts them and shows the total number of days, plus the same period in weeks, months and years.
Does the calculator include the end date?
Not by default. Choose "Yes, add 1 day" to include both the start and end dates, which is common for leave and event lengths.
How are weekdays counted?
Weekdays are Monday to Friday between the two dates (following the same include or exclude rule for the end date). Public holidays are not removed.
Does it handle leap years?
Yes. The calculator uses real calendar dates, so 29 February is counted in leap years and months of 28, 29, 30 or 31 days are handled correctly.
Can the end date be before the start date?
Yes. The calculator still shows the size of the gap and notes that the end date is earlier than the start date.