Age & Date Calculator

Calculate exact age in years, months and days from a date of birth, along with totals in weeks, days and hours and a countdown to the next birthday.

How age is calculated

Age is measured in completed years, months and days rather than as a decimal. Someone born on 15 March 1990 turns 36 on 15 March 2026 — not partway through, and not on any other date. The month arithmetic handles varying month lengths correctly. Counting from 31 January to 28 February gives 28 days rather than rolling into an invalid 31 February, which is a common source of off-by-a-day errors in simpler calculators.

Leap years and 29 February

Anyone born on 29 February has a birthday that exists only every four years. There is no universal rule for which date they "become" a year older in common years, and jurisdictions genuinely differ — some treat 28 February as the anniversary, others 1 March. This calculator counts completed years from the birth date, which is the mathematically consistent approach. For legal purposes such as age of majority, the applicable local rule takes precedence over any calculator.

Practical uses

Beyond curiosity, exact age matters for eligibility thresholds — school entry, retirement, insurance bands and visa requirements often hinge on age at a specific date rather than in the current year. The total-days figure is useful for milestone planning, and the countdown is handy for anyone organising events. Note that all calculations use your device's clock and local timezone, so a device with an incorrect date will produce an incorrect result.

Quick tips

• Results depend on your device clock — check it if a figure looks wrong.
• For legal age thresholds, confirm the applicable local rule rather than relying on any calculator.
• Dates are processed in your browser and never transmitted.
• Use the total-days figure for milestone anniversaries such as 10,000 days.

Does this account for leap years?

Yes, full date math precision is maintained including leap year calculations.