Working
The calculator measures from the earlier date of birth to the later one: full calendar years first, then full months, then the remaining days.
28 Sep 1982 → 28 Sep 1992 = 10 years
28 Sep 1992 → 28 Feb 1993 = 5 months
28 Feb 1993 → 15 Mar 1993 = 15 days
Age gap = 10 years, 5 months and 15 days = 3,821 total days.