Calculate your exact chronological age with our free Age Calculator. Compute years, months, days, total weeks, hours, seconds, Western Zodiac signs, Chinese Zodiac animal years, and countdowns to your next birthday with 100% offline privacy and automatic leap-year boundary handling.
Select your month, day, and year of birth using the date picker.
Select the calculation date (defaults to the current day).
View your exact age in years, months, days, total hours, and birthday countdowns.
Uses calendar-aware borrow algorithms (adjusting for 28, 30, and 31-day months) to calculate human chronological age accurately.
Calculates remaining months and days until your next birthday anniversary milestone.
All calculations execute in browser JavaScript memory. Birth dates are never transmitted to external analytics or databases.
Determining chronological age is more complex than simply dividing total elapsed milliseconds by a standard year duration (\(365.2425 \text{ days}\)). Because Gregorian calendar months vary between 28, 29, 30, and 31 days, accurate age algorithms step through calendar unit boundaries.
When target days are fewer than birth days, the algorithm borrows the exact number of days in the preceding target month (days += prevMonth.getDate()) and decrements the month count. Similarly, if target months are fewer than birth months, 12 months are borrowed from the target year.
For leap year births on February 29th, the engine evaluates whether the target year is a leap year (\(\text{Year} \pmod 4 = 0 \land (\text{Year} \pmod{100} \neq 0 \lor \text{Year} \pmod{400} = 0)\)), advancing age on March 1st during common 365-day years.