Calculate the difference between two time values

Problem/Question/Abstract:

How to get the hours and minutes between two DateTime values?

Answer:

Solve 1:

In order to avoid future questions about rounding, I would consider the solution below (untested!):

{ ... }
var
  InTime, OutTime: TDateTime;
  InMinutes, OutMinutes, MinutesDiff: Int64;
  DiffHours, DiffMinutes: Integer;
begin
  { First, make sure that InTime and OutTime are relative to the same offset from GMT. Then:}
  InMinutes := round(InTime * 24 * 60);
  OutMinutes := round(OutTime * 24 * 60);
  MinutesDiff := OutMinutes - InMinutes;
  Assert(MinutesDiff >= 0);
  DiffHours := MinutesDiff div 60;
  DiffMinutes := MinutesDiff mod 60;
end;


Solve 2:

{ ... }
var
  InTime, OutTime, TimeDifference: TDateTime;
  DiffHours, DiffMinutes: Integer;
begin
  TimeDifference := OutTime - InTime;
  {ShowMessage(DateTimeToStr(TimeDifference);}
  DiffHours := trunc(TimeDifference * 24);
  { DiffMinutes := trunc((TimeDifference * 24 * 60) - (Trunc(TimeDifference * 24) * 60))}
  DiffMinutes := trunc((TimeDifference * 24 * 60) - (DiffHours * 60))
end;