Age Calculator
Calculate your age in years, months, and days from your date of birth. Use today or choose another reference date, then see total days and the countdown to your birthday.
Your age
Birthday on or after the reference date
How to use the age calculator
- Enter your complete date of birth.
- Choose the date on which you want to calculate your age. Use Today fills in your device’s current local date.
- If you were born on February 29, choose the anniversary convention for non-leap years.
- Select Calculate Age. Read your completed years, remaining months and days, and total elapsed days.
- Use Copy Results if you want to keep a text summary.
What does years, months, and days mean?
The result starts with completed calendar years. It then counts completed months after that anniversary and the remaining days. Months are calendar months, not fixed blocks of 30 days. Total days is a separate count of the actual days between the two dates.
For example, someone born on May 10, 2000 is 25 years, 0 months, and 5 days old on May 15, 2025. Their completed age in years is 25; the extra five days do not add another year.
Leap years and February 29 birthdays
The calculator uses the Gregorian calendar, including century-year rules. A year divisible by 4 is a leap year, except century years unless they are divisible by 400. This means 2000 was a leap year and 1900 was not.
For a February 29 birth, choose February 28 or March 1 as the anniversary in a non-leap year. This changes the completed-year result around the anniversary and the birthday countdown. The number of actual elapsed days stays the same. The setting describes a calculation convention; it does not determine legal age rules for a particular place.
Why can month-end calculations differ?
Calendar months have different lengths. This calculator first counts completed years using the chosen anniversary, then adds months from that anniversary. If a target month lacks the starting day, the month is clamped to its last day. January 31 to February 28, 2025 is therefore one completed month.
This convention is stated because another calculator might borrow days from the previous month or use a different month-end rule. When a form asks only for completed years, use the years value. When it asks for an age on a deadline, set that exact reference date.
Total days, weeks, and completed months
Total days counts the interval between the date of birth and the reference date, without counting the starting date as an extra day. Weeks are seven-day groups, with the remainder shown separately. Completed months combines the years and months from the calendar-age result.
The calculator does not know the time of birth. It does not report precise lived hours, minutes, or seconds. Calendar-date calculations use midnight-based UTC dates internally so daylight-saving changes do not add or remove a day.
Birthday countdown and future dates
The birthday panel finds the first birthday on or after the reference date. On a birthday itself, the countdown is zero. If you choose a future date, the countdown is measured from that future date, rather than from today. Dates before birth are rejected.
Your date stays in the calculator
The calculator’s code processes the entered dates in your browser. It does not send the date of birth to a calculation server or require an account. Verify dates before using results on a form, especially if you are checking a fixed eligibility date.
Frequently asked questions
How do I calculate my age on a specific date?
Enter your date of birth and set Age on this date to the required reference date. The result is measured on that date, even if it is in the past or future.
Does the calculator account for leap years?
Yes. Actual calendar dates are used, including February 29 and the Gregorian century-year rules.
What happens if I was born on February 29?
Choose February 28 or March 1 as the anniversary in a non-leap year. The setting affects completed age around that date and the birthday countdown.
Why is my birthday countdown zero?
The reference date is your birthday under the selected convention. The panel includes a birthday occurring on the reference date itself.
Can I calculate a baby’s age in days?
Yes. Total days shows the elapsed days from birth to the selected date. A birth and reference date that are the same give zero days.
Is this a legal age determination?
No. The tool calculates calendar age. Use the rules and reference date specified by the relevant organization or authority.
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