Completed years are not the same as elapsed days divided by 365. Use an explicit birth date and as-of date, and confirm which anniversary convention your process requires.
Use actual date values
With the birth date in A2 and the as-of date in B2, =DATEDIF(A2,B2,"Y") returns whole years between those dates. Format the result as a number.
Check that both inputs are valid dates with the intended day and month. A display format cannot correct a birth date that was interpreted incorrectly during import.
Choose a fixed or current reference date
For a historical report, use a fixed, labeled as-of date rather than TODAY. TODAY changes as the spreadsheet recalculates, so a report can show different ages when reopened later.
Reject or flag future birth dates and missing inputs explicitly. Do not suppress those conditions by returning a plausible age or zero. An age of zero can be valid for an infant and should not double as an unexplained error label.
Check anniversary boundaries
Test the day before a birthday, the birthday itself, and the following day. Review leap-day cases against the policy governing your application. A spreadsheet calculation does not itself define a legal eligibility rule.
Keep personal dates appropriately restricted and avoid copying real birth dates into public examples or third-party debugging services. If only an age band is required, consider an authorized output containing that band rather than distributing the complete source dates. Document the as-of date and the calculation convention so readers can reproduce the result without assuming it is permanently current.
References
Reviewed against the linked official product guidance on November 3, 2026. Features, limits, screen labels, and access can vary by account, platform, region, and organization policy.