Your Exact Age
Years
Months
Days
Next Birthday:
🎂 How the Age Calculator Works
Age calculation seems trivial, but leap years and variable month lengths make exact day-level precision tricky. Here's how the tool handles it.
Age = Today − Date of Birth (using calendar arithmetic)
Days = Math.floor((today − dob) / 86400000)
Leap Year: year % 4 === 0 && (year % 100 !== 0 || year % 400 === 0)
1
Both dates are converted to Unix timestamps (milliseconds since Jan 1 1970). The difference gives total elapsed milliseconds.
2
Exact years are calculated by stepping year-by-year from DOB, accounting for whether each year is a leap year (366 days) or not (365 days).
3
The remaining months and days are resolved using the actual days-in-month for that specific calendar month (e.g. February has 28 or 29 days).
Example: DOB = March 15, 1990 → Today = May 5, 2026.
Full years = 36 | Remaining months = 1 | Remaining days = 20
Total days lived ≈ 13,200+ days
Full years = 36 | Remaining months = 1 | Remaining days = 20
Total days lived ≈ 13,200+ days
JavaScript's Date object handles DST and timezone edge cases automatically.