function DateTimeToMilliseconds(const ADateTime: TDateTime): Int64; //获得毫秒
var
LTimeStamp: TTimeStamp;
begin
LTimeStamp := DateTimeToTimeStamp(ADateTime);
Result := LTimeStamp.Date;
Result := (Result * MSecsPerDay) + LTimeStamp.Time;
end;
原文：http://www.cnblogs.com/delphi-xe5/p/5400207.html