Age Calculator
Find your exact age in years, months, days, hours, and seconds. See when your next birthday lands and what day of the week you were born.
Runs in your browser — nothing uploaded
Dates
Find your exact age — not just in years, but in months, days, hours, minutes, and seconds. Useful for filling out forms that ask for age in a specific unit, for working out an age on a past date (a wedding, a milestone, a passport renewal), or for the small joy of knowing you're about to roll over a round-number day count.
Private by design — your data never leaves your device
How to use it
No account, no upload — it all happens on your device.
1
Type or pick your date of birth using the date field.
2
Leave the 'Age at' date set to today, or change it to find your age on any past or future date.
3
Read your age in years, months, and days — plus weeks, days, hours, minutes, and seconds in the panel below.
4
Scroll down to see the day of the week you were born and how long until your next birthday.
What this calculator does
Three numbers, then the details.
| Output | How it's worked out | Example |
|---|---|---|
| Years / months / days | Calendar subtraction, leap years included | 1990-03-15 → today = 36 yr, 2 mo, 23 d |
| Total days / hours / seconds | Real milliseconds between the two dates | ≈ 13,232 days, ≈ 1.14 billion seconds |
| Next birthday | Next anniversary of your birth date | In 102 days — you'll turn 37 |
Common reasons to look up an exact age
- Forms and applications that ask for an age in completed years on a specific date — visas, school registrations, insurance.
- Medical and legal contexts where months and days matter (paediatric dosing, age-of-majority cut-offs).
- Pets — convert their birthday into days or weeks for vaccination schedules.
- Milestones— "you've been alive for a billion seconds" lands around your 31st birthday.
Pitfalls
- Leap-year birthdays.29 February only happens in leap years. On non-leap years this calculator treats your birthday as 1 March for the "next birthday" field (the same convention most countries use legally).
- Time zones. Dates are interpreted in your local time zone. Someone born in Tokyo and someone in Los Angeles using the same birth date will see the same result — the moment-of-birth precision needed to differ rarely matters in everyday use.
- Hours and seconds drift. Without a time of birth, the live seconds counter assumes midnight. For exact second counts on milestone moments, factor in your actual time of birth.
Frequently asked
How is age calculated?
Years are counted first, then leftover months, then leftover days. The calendar handles months of unequal length and leap years, so 28 Feb 2020 to 28 Feb 2021 is exactly 1 year — and 29 Feb 2020 to 28 Feb 2021 is 11 months and 30 days.
Why is my age in days different from years × 365?
Years are 365 or 366 days because of leap years, so multiplying by 365 underestimates the day count. The calculator works out the exact number of days between the two dates using the calendar, not an average.
Does my birth date go to a server?
No. Everything is calculated in your browser as plain arithmetic — your birth date is never uploaded, stored, or shared.