“Age from date” may mean completed years, or a duration in years, months, and days. Enter a known start date and compare the output before, on, and after its anniversary. Then test a month-end start and a leap-day start to see how the tool handles dates that do not recur every year.
If the result depends on the present moment, record the date and time zone used in the calculation rather than assuming everyone sees the same day. For a reproducible report, provide the input date, reference date, selected zone, expected counting convention, and actual display.
Akousa