How age is calculated
Age is counted in whole calendar months first and then the days left over, the same way people say it out loud. For example, from 31 January to 1 March is one month and one day. Leap years are taken into account, so total days are exact.
If you were born on 29 February, your next birthday in a non-leap year is shown as 28 February, the date most people celebrate on.
Useful for forms and planning
Many applications ask for your age on a specific date, such as the closing date of a job advert or the start of a school year. Set the second date to that day to get the exact answer. You can also use it to work out the time between any two dates, like the age of a company or the length of a project.