How old, exactly?

Exact age, to the day

Age in years is what forms ask for. Age in years, months and days is what actually describes how long someone has been alive, and the difference matters for development milestones and for anything with an age cutoff.

1. Enter the date of birth. Any date in the past. The tool handles leap days correctly, which matters for people born on 29 February — their legal age advances on 28 February or 1 March depending on the jurisdiction.
2. Leave the second date at today, or set it. Setting a different date answers "how old will I be on that day", which is the useful form for planning a birthday, a retirement date, or an eligibility cutoff.
3. Read the breakdown. Years, months and days, plus the totals in months, weeks and days. The totals are what you need when a form asks for age in months, which is common for young children.

When this comes up

• Filling in a form that wants exact age. Visa applications, school admissions and some medical questionnaires ask for age in years and months, and rounding is not accepted.
• Checking an age cutoff. Whether someone is old enough on the day of an event, not on the day of registration, is a recurring problem in sport and in travel.
• Tracking a child’s development. Milestones in the first two years are measured in months, and the difference between 18 and 20 months is clinically meaningful.
• Working out a retirement or pension date. Setting the reference date forward shows exactly when a threshold is crossed.

Questions