Date tools
Each one runs entirely in your browser — nothing you type is sent anywhere — and each page explains the rule that usually trips the calculation up.
- Days between two datesCount the days, weekdays and weekend days between any two dates, in either direction.
- Age calculatorWork out an exact age in years, months and days, plus the total days lived and the next birthday.
- Business day calculatorAdd or subtract business days, skipping weekends and US federal holidays.
- Week numberThe ISO 8601 week number for any date, with the week-numbering year.
- Leap year checkerWhether any year is a leap year, and why.
How old am I if I was born in…
A birth year gives two answers, not one — your age before your birthday and after it. Each year has its age in every year around this one, the milestone birthdays still ahead, and how many days that is.
What year was I born if I’m…
The same question from the other end, answered with the birth-date range rather than a year: the boundary falls mid-year, so an age spans two of them.
How many days in a month
A named month of a named year needs the calendar, not a conversion factor. Pure unit conversions — hours to days, weeks to days — are the same arithmetic everywhere.