birth date → age
Age calculator
A person born on 15 June 1990 is 35 years, 6 months and 17 days old on 1 January 2026, which is 12984 days. Enter a date of birth, and change the age-on date if you want another day.
- 1990-06-15 → 2026-01-01 = P35Y6M17D
- 1990-06-15 → 2026-01-01 = 12984 d
- 2000-02-29 → 2026-03-01 = P26Y
The age-on date starts as today on your device's clock. Change it to find an age in the past or the future. The dates are not stored or sent anywhere.
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At a glance
- Price
- No charge
- Account
- None needed
- Upload
- Not applicable — you type dates, nothing is sent anywhere
- Age rule
- Completed years, then whole months, then days
- 29 February
- Birthday reached on 1 March in a common year
- Date range
- 0001-01-01 to 9999-12-31, Gregorian calendar
Days lived and 29 February birthdays
These tables use the same functions as the calculator. The first assumes a birth on 1 January 2000 and counts to the birthday itself.
| Age in years | Days lived | Whole weeks lived |
|---|---|---|
| 1 | 366 | 52 |
| 10 | 3653 | 521 |
| 18 | 6575 | 939 |
| 21 | 7671 | 1095 |
| 30 | 10958 | 1565 |
| 50 | 18263 | 2609 |
| 65 | 23742 | 3391 |
| 100 | 36525 | 5217 |
| Year | Leap year | Birthday counted on | Weekday number (1 = Monday) |
|---|---|---|---|
| 2023 | – | 2023-03-01 | 3 |
| 2024 | ✓ | 2024-02-29 | 4 |
| 2025 | – | 2025-03-01 | 6 |
| 2026 | – | 2026-03-01 | 7 |
| 2028 | ✓ | 2028-02-29 | 2 |
How to find an exact age
Enter the date of birth
Use the date picker, or type the date as YYYY-MM-DD, for example 1990-06-15. A date that does not exist, such as 2023-02-30, is refused with a message.
Choose the age-on date
The second date starts as today. Change it to see how old someone was on a past day, or how old they will be on a future one. It cannot be earlier than the date of birth.
Read the age
You get the age in years, months and days, and the same span as total days, weeks and months. The next birthday is shown with its weekday and the number of days left.
How the age is calculated
Whole years are the number of birthdays that have passed. The months are the whole months since the last birthday, and the days are what remains after those months. The total days are the exact difference between the two dates on the Gregorian calendar, counted in UTC so a daylight saving change never adds or removes a day. A person born on 1 January 2000 has lived 9797 days on 28 October 2026. The weeks are those days divided by 7, rounded down.
A birthday on 29 February is treated as reached on 1 March in a common year, and on 29 February in a leap year. So someone born on 29 February 2000 turns 26 on 1 March 2026. Other rules exist, and some countries use 28 February in law, so check the rule that applies to you. This calculator counts completed years, which is the usual way to state an age in most of the world; some traditional systems count a baby as 1 at birth and are not used here. Dates run from 0001-01-01 to 9999-12-31.
Age calculator questions
How old am I in days?
Count the days from your birth date to the date you choose. Someone born on 1 January 2000 is 366 days old on 1 January 2001, 3653 days old at 10 years and 9797 days old on 28 October 2026. The calculator shows this number, the weeks and the months for any birth date.
How is exact age in years, months and days worked out?
Take the last birthday, count the whole months since it, then count the days left over. From 15 June 1990 to 1 January 2026 that gives 35 years, 6 months and 17 days. If the birthday has not come yet this year, the years are one lower.
When is a 29 February birthday reached in a common year?
This calculator treats 1 March as the birthday in years that have no 29 February, so a person born on 29 February 2000 is 25 on 28 February 2026 and turns 26 on 1 March 2026. In a leap year such as 2028 the birthday is 29 February itself.
How many days until my next birthday?
The next birthday tile shows the date, the weekday and the days remaining. If the age-on date is itself your birthday, the answer is 0 days and the date shown is that day. A birthday on 15 June 2026 falls on a Monday.
How old will I be on a future date?
Type the future date into the age-on field. The age shown is how old you will be on that day, in years, months and days, assuming the date is not before your birth date.
Why do two age calculators sometimes disagree by a day?
They may count differently, for example by including both the birth day and the end day, by using local time near midnight, or by handling the months in another way. This calculator counts the days from the birth date to the chosen date without including the birth day, and works on calendar dates, not clock times.