ExpandDate
function ExpandDate (D : Word) : TDateTime;
ExpandDate translates an OnGuard date offset to an actual date.
OnGuard uses a date offset to reduce the amount of space necessary to store a date. OnGuard creates a date offset by subtracting the TDateTime value for 1 January 1996 from the actual date.
Exceptions to the conversion rules are that a value of 0 expands to 1 January 9999 and date offsets larger than 65535 are represented as 0 (anything after 6 June 2175).
This routine is defined in the OnGuard unit. (as of 1.15 this routine has been moved to the OgUtil unit)