How age is counted
Age is counted in completed years, months and days. Someone born on May 15, 1990 turns 36 on May 15, 2026; on October 17, 2026 they are 36 years, 5 months and 2 days old. A month counts once the same day of the month comes round again, which is why ages and contract terms do not simply divide days by 30.
More than just years
The same person has been alive for 13,304 days, or 1,900 full weeks, and was born on a Tuesday. Their next birthday is 210 days away. Totals in days are handy for milestones such as a 10,000-day party (about 27 years and 4 months).
Leap-day birthdays
If you were born on February 29, you have a real birthday only every four years. In other years this calculator uses February 28, which is what many US states and other countries use to decide when someone legally comes of age; some places use March 1 instead.
Other uses
Set the "as of" date to see how old someone will be on a future date (for school entry, retirement or eligibility rules) or was on a past date.
How this works
The page counts whole months from the date of birth to the target date, taking one month off if the day of the month has not been reached yet. Twelve months make a year, and the remaining days are counted from the last monthly anniversary. Totals of weeks and days come from the exact number of days between the two dates. All dates are handled as calendar days, so time zones cannot shift the result.
Frequently asked
How do I calculate my exact age?
Count completed years, then completed months, then the remaining days since your last monthly anniversary.
How many days old am I?
Enter your date of birth: the page shows the total number of days, weeks and months.
What day of the week was I born?
The page shows the weekday of your date of birth.
How are February 29 birthdays handled?
In common years the birthday is taken as February 28.
Sources
Reviewed Oct 17, 2026 · test vectors fixtures/calculators/date/age-calculator/