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Age Calculator computes the exact age from a date of birth to today (or any target date), showing years, months, days, hours, minutes, and seconds. It also calculates days until the next birthday, the day of the week you were born, how many days you have lived, and the equivalent in other time units. All calculations happen in your browser — no data is sent anywhere.
Age calculation sounds simple but has edge cases: February 29 birthdays (leap day babies age once every 4 years under strict interpretation, but most systems count March 1 in non-leap years), month-end calculations (January 31 + 1 month = ?), timezone considerations for international birthdays, and the difference between completed years vs the fraction of the next year started. This calculator uses standard calendar conventions.
Precise age calculations matter in many contexts: legal age requirements (voting, drinking, driving, retirement), medical dosing (pediatric medications are weight and age based), school enrollment deadlines, social media minimum age requirements, insurance policies with age bands, and financial calculations (early retirement penalties, Social Security eligibility).
Born January 15, 1990
Result: Age: 36 years, 6 months, 11 days (as of July 26, 2026) / Days lived: 13,371 / Born on: Monday
Days until next birthday
Result: If birthday is August 20: 25 days until next birthday (August 20, 2026)
Leap day birthday (Feb 29, 1992)
Result: Strict age: turns 8 on Feb 29, 2000 (only counts leap years) / Common: turns 34 in 2026 (March 1 in non-leap years)
How is age calculated across months with different lengths?
Standard age calculation: add the years until you reach the same month-day in the target year, then add remaining months, then remaining days. January 31 + 1 month = February 28/29 (the last day of February, since Feb doesn't have 31 days). This is how most legal and medical age calculations work.
When is a leap day baby's birthday?
This varies by jurisdiction and context. Most countries legally recognize February 28 as the birthday in non-leap years (the day before March). Some recognize March 1. The legal age for voting, driving, and other purposes follows local jurisdiction rules. This calculator uses February 28 for non-leap years.
What day of the week was I born?
The day of the week for any date can be calculated using Zeller's congruence or the Tomohiko Sakamoto algorithm. This calculator shows the day name for your birth date. Knowing your birth day is useful for superstitions, astrology, and as a fun fact.
How old is someone in years, months, and days?
This requires careful month-by-month counting. Subtract the years, then count how many complete months have passed in the partial year, then count remaining days. The 'months' component accounts for variable month lengths — the result is not simply total days / 30.
How many seconds old am I?
Approximately: (years × 365.25 × 24 × 3600) + adjustments for actual calendar. A 36-year-old has lived roughly 1.136 billion seconds. For a precise count, the calculator uses actual calendar dates with leap year handling rather than the 365.25 approximation.