function HourOfTheWeek(const AValue: TDateTime): Word;
unsigned short __fastcall HourOfTheWeek(System::TDateTime AValue);
Returns the number of hours between a specified TDateTime value and 12:00 A.M. of the first day of the week.
Call HourOfTheWeek to obtain the number of complete hours between AValue and 12:00 A.M. on Monday of the week that includes AValue.
Note: HourOfTheWeek defines the week of AValue according to the ISO 8601 standard. That is, the week starts on Monday and ends on Sunday.