Compares two TCustomPgTimeStamp objects.
function Compare(Value: TCustomPgTimeStamp): integer; virtual; abstract;
Call the Compare method to compare two TCustomPgTimeStamp objects.
If the current object represent date and time that is greater than Value, Compare returns a positive number.
If the current object represent date and time that is lower than Value, Compare returns a negative number.
If the current object equals to Value, Compare returns 0.