Calculate age — or the interval between any two dates — in years, months, weeks, days, hours, minutes, and seconds.
This calculator uses the most common Western convention: age increases by one on each birthday. Someone who has lived 3 years and 11 months is "3 years old" until their next birthday, one month later.
Months have different lengths, so counting "how many months and days" between two dates isn't always intuitive. From Feb 28 to Mar 31, for example, this calculator counts Feb 28 to Mar 28 as one full month, leaving 3 remaining days — a different (but equally reasonable) convention than treating both as "end of month" and calling it exactly one month.
Yes — "Date of Birth" and "Age at the Date of" are just labels; enter any two dates to see the full interval broken down every way.
It doesn't — "total months" is exactly years×12 plus the leftover months, paired with the same leftover days as the main year/month/day result.
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