Age and days-between-dates calculator
Find out your exact age in years, months and days, how many days you have lived and how long until your next birthday. You can also work out the days between any two dates.
How exact age is worked out
Working out an age looks as easy as subtracting the birth year from the current year, but that sum almost always fails: it ignores whether you've already had your birthday this year. If you were born on 10 November, then today, 22 June, you haven't had it yet, so you're a year younger than the year subtraction suggests. This tool compares the full date, which is why it gives your real age, not a rough one.
Years, months and days, not just years
Sometimes years aren't enough. For a baby you talk in months; for a form, you might need the exact number of days. The calculation works down from largest to smallest: first the complete years, then the months since your last birthday, and finally the leftover days. That's where the months come in, since they aren't all the same length (28, 30 or 31 days), along with leap years and their 29 February. Doing it by hand is exactly where most people slip up.
The curious case of 29 February
Anyone born on 29 February only gets that exact date once every four years. In ordinary years their birthday is usually moved to 28 February or 1 March, depending on the convention used. It's a minor detail for most purposes, but it explains why an age calculation can shift by a day around that date.
What it's used for
Beyond curiosity, it's handy for very concrete things: checking whether someone has reached the age of majority or retirement age, seeing how long until a key date, working out length of service in a job, a gestational age in weeks, or simply how many days you've been alive. The whole calculation happens in your browser; the date you enter isn't sent anywhere.