Age Calculator (Years, Months, Days from Date of Birth)
Exact age in years, months and days — plus total days lived and days until next birthday.
Result
Exact Age
26 yrs, 4 mo, 14 days
Born on
Saturday
Total Days
9,631
Total Weeks
1,375
Total Hours
231,144
Next Birthday in
231 days
Concept
Age calculation is not simple subtraction because months have different lengths (28–31 days) and leap years add an extra day to February. Naively subtracting calendar dates gives the wrong answer whenever the birthday has not yet passed in the current year, or when months with different lengths are involved.
The correct approach uses a year–month–day hierarchy: first count complete calendar years, then complete months in the remaining period, then remaining days. When the day or month component goes negative, you borrow from the next-larger unit — exactly like carrying in elementary subtraction.
Civil age (used in most legal contexts) follows the birthday-has-passed rule: you are considered N years old from your Nth birthday until the day before your (N+1)th birthday. This is distinct from fractional or decimal age, which divides the exact elapsed time in days by the mean year length.
Formula
Variables
DOB- Date of Birth — the start reference point.
Ref- Reference date — defaults to today, can be any past or future date.
Years- Complete calendar years elapsed between DOB and Ref.
Months- Complete months remaining after full years are counted.
Days- Remaining days after full years and months are counted.