Age, Countdown & Date Calculator

Find your exact age, count down to any date, list 100-day and yearly anniversaries, add days to a date, or count the days between two dates — all in one place.

Date of birth

As of (usually today)

How age is calculated

Your age increases by one on each birthday, starting from 0 on the day you were born. If you were born on 29 February, the calculator treats 1 March as your birthday in non-leap years (some countries use 28 February — the difference is one day).

Counting anniversaries

By default the start date is day 0, so "100 days" is exactly 100 days later — the usual rule for deadlines and contracts. Couples in Korea, Japan and Taiwan often count the first day as day 1, which makes the 100th day 99 days after the start; tick "Count the start date as day 1" for that style.

FAQ

Does "days between" include both dates?

Not by default: from Monday to Friday is 4 days. Tick "Include the end date" to count it as 5, as you would for a hotel stay counted in days or a leave request.

Are public holidays excluded from business days?

Only Saturdays and Sundays are excluded. Holidays differ by country and year, so subtract them yourself.