Formula
The day count is divided by the mean Gregorian year:
Decimal years = days lived / 365.2425
The age page shows calendar years, months, and days instead of one decimal.
Assumptions
- The as-of date is on or after the birthday.
- 365.2425 days is the year length.
Worked example
From March 15, 1994 to October 14, 2026 is 32.58 decimal years.
Input definitions
- As of
- The date the age is measured on.
Limitations
A decimal year is not the same as a birthday age in years and months.
Questions
Why 365.2425?
It is the average length of a Gregorian year, including leap years.
Where is the years-and-months age?
The age calculator keeps calendar years, months, and days.