How to calculate age
Enter a birth date and the comparison date requested by the workspace. The calculator returns a calendar age using years, months, and days, plus supporting day-based information where shown. The calculation runs locally in the browser.
Calendar age is not total days divided by 365
A calendar year can have 365 or 366 days and calendar months have different lengths. “30 years, 2 months, 5 days” is therefore not calculated by dividing an elapsed-day count by fixed 365-day years and 30-day months.
The processor advances through real calendar boundaries. That makes the result useful for ordinary age questions while keeping total elapsed days as a separate concept.
Leap-day birthdays need a stated rule
For a February 29 birth date, non-leap years do not contain the same month/day combination. This calculator uses its documented clamped calendar rule when advancing through those years. If an institution, jurisdiction, insurance policy, or eligibility program defines a different legal rule for leap-day birthdays, that external rule is the authority.
Example: birthday not reached yet
Suppose a person was born on October 20 and the comparison date is September 7 in a later year. Simply subtracting the year numbers would overstate the completed calendar age by one year because the October birthday has not happened yet. The calculator accounts for the month and day rather than only the year field.
Age versus date difference
Use this tool when the starting date represents a birth date and you want an age-style calendar answer. For two arbitrary project, travel, contract, or event dates, use the Date Difference Calculator instead.
Boundaries and privacy
Dates are validated as real calendar dates within the supported year range. Future birth dates are rejected for age calculation. The inputs are processed locally and are not uploaded for the calculation.
A date alone can still be sensitive in context, so use the same device and browser care you would use for other personal information. The browser-local processing guide explains what the local-processing label covers.