How to use the Date Difference Calculator tool
- Pick two datesChoose a start and an end date. Tick “Include time of day” to compare exact times too.
- Decide on the end dateTick “Include the end date” to count both the first and the last day, as for holidays or contracts.
- Read the differenceSee it as years, months and days, plus total days, weeks, business days, hours, minutes and seconds.
- Or add / subtractSwitch to “Add or subtract days” to find the date a number of days, weeks, months or years away.
Features
- Exact calendar mathHandles leap years and months of different lengths correctly.
- Business daysCounts Monday to Friday automatically, and can add or subtract business days.
- Inclusive countingChoose whether the end date counts, so “Monday to Friday” can be 4 or 5 days.
- Time of dayCompare exact date-times down to the minute.
- No time-zone surprisesCalculations ignore daylight-saving changes, so a day is always a full day.
How the difference is calculated
The calculator first counts whole calendar months from the start date, then the remaining days. So 15 January to 20 March is 2 months and 5 days. When a month doesn’t have the same day number, it uses the last day of the month: one month after 31 January is 28 February (or 29 in a leap year). This matches how most people, contracts and HR systems count months.
Should the end date be included?
By default, the calculator counts the days between the dates: from Monday to Friday is 4 days. Many real-life questions count both ends: a hotel booking, a leave request from Monday to Friday (5 days), or a contract running from 1 January to 31 December (365 days). Tick Include the end date for those cases.
Business days
Business days (also called working days) are Monday to Friday. They are used for delivery times, payment terms, notice periods and legal deadlines. For example, “payment within 10 business days” from a Friday ends two weeks later on a Friday. Public holidays vary by country and region, so they are not subtracted automatically; remove them yourself if they apply.
Useful facts
| Period | Length |
|---|---|
| Common year | 365 days, 52 weeks and 1 day |
| Leap year | 366 days (every 4 years, except century years not divisible by 400) |
| Average month | 30.44 days |
| Quarter | 90–92 days |
| Business days per year | About 260 (before public holidays) |
Popular uses
- Days until a birthday, wedding, exam, holiday or product launch.
- Length of employment, a rental contract or a subscription.
- Due dates: 30, 60 or 90 days from an invoice date.
- Pregnancy and project timelines in weeks and days.
Want to know someone’s exact age? Use the Age Calculator. To convert a Unix timestamp to a date, use the Timestamp Converter.