Converters
Days between two dates, business days and age
Choose what to work out: the days between two dates with the weekdays from Monday to Friday, an exact age from a date of birth, or the date that falls a number of calendar or business days after another.
Counting the days between two dates
Counting days by hand is easy to get wrong: months differ in length, leap years add 29 February, and you must decide whether the first and last days count. The convention here is the one used for deadlines: from 1 January to 31 December 2024 there are 365 days; counting the end date as well makes 366, every day of the leap year.
Business days leave out Saturdays and Sundays. In 2025 there are 261 days from Monday to Friday. Public holidays are left to you, because they depend on the country and often on the region: take off the ones that fall on a weekday where you live, or see the other language versions of this page, which remove the national holidays of their country.
An age is counted in whole months and then days, as on a calendar: from 31 January to 1 March is one month and one day. Someone born on 29 February has their birthday on 28 February in common years.
Common mistakes
- Not deciding whether the end date counts: a stay from the 10th to the 15th is 5 nights but involves 6 calendar days.
- Treating bank holidays and office closures as business days: the calculator removes weekends only.
- Counting months as a fixed 30 days: between real dates months vary, and the error builds up.
Frequently asked questions
Does the calculation handle leap years?
Yes: dates are handled as real calendar days, so 29 February exists in leap years and is missing in the others.
Why are public holidays not removed?
Because they differ between the UK, the US, Ireland, Australia and every other English-speaking country, and often between regions. The count of weekdays is exact; subtract your local holidays from it.
How do I find a deadline 30 business days away?
Choose “Date after N days”, enter the start date and 30, and set business days: the calculator skips weekends and also shows how many calendar days go by.
How this calculation works
Dates are turned into whole days since 1 January 1970 in UTC, so daylight saving time never changes a count. Difference = end day − start day (+1 when the end date counts). Years and months: the largest number of whole months that can be added to the start date without passing the end date, with the day moved to the month's end when it does not exist; the rest is days. Business days: Monday to Friday.