FileMaker Pro Custom Functions

// This is a Custom Function version of calculations provided in "Advanced FileMaker Pro 5.5" by Chris Moyer and Bob Bowers. This formula differs slightly from the ones in the book which do not account for leap years. Let ( leapFactor = If ( Mod ( Year ( theDate ) ; 4 ) = 0 ; 1 ; 0 ); Case ( // Age in years Format = 1 ; Year ( theDate ) - Year ( Birth ) - ( ( DayOfYear ( theDate ) - leapFactor ) < DayOfYear ( Birth ) ); // Age in years and days Format = 2 ; Year ( theDate ) - Year ( Birth ) - ( ( DayOfYear ( theDate ) - leapFactor ) < DayOfYear ( Birth ) ) & " years and " & Case ( ( DayOfYear ( theDate ) - leapFactor ) ≥ DayOfYear ( Birth ) ; DayOfYear ( theDate ) - leapFactor - DayOfYear ( Birth ) ; DayOfYear ( theDate ) + ( DayOfYear ( Date ( 12 ; 31 ; Year ( theDate ) ) - DayOfYear ( Birth ) - leapFactor ) ) ) & " days" ; // Age in years, months and days Format = 3 ; Year ( theDate ) - Year ( Birth ) - ( ( DayOfYear ( theDate ) - leapFactor ) < DayOfYear ( Birth ) ) & " years and " & Mod ( Month ( theDate ) - Month ( Birth ) + 12 - (Day ( theDate ) < Day ( Birth ) ) ; 12 ) & " months, and " & (theDate - Date ( Month ( theDate ) - (Day ( theDate ) < Day ( Birth ) ) ; Day ( Birth ) ; Year ( theDate ) ) ) & " days" ) )
 Then copy & paste into FileMaker Advanced's Edit Custom Function window.