Author: Lou Adler

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!):

1   { ... }
2   var
3     InTime, OutTime: TDateTime;
4     InMinutes, OutMinutes, MinutesDiff: Int64;
5     DiffHours, DiffMinutes: Integer;
6   begin
7     { First, make sure that InTime and OutTime are relative to the same offset from 
8   GMT. Then:}
9     InMinutes := round(InTime * 24 * 60);
10    OutMinutes := round(OutTime * 24 * 60);
11    MinutesDiff := OutMinutes - InMinutes;
12    Assert(MinutesDiff >= 0);
13    DiffHours := MinutesDiff div 60;
14    DiffMinutes := MinutesDiff mod 60;
15  end;



Solve 2:

16  { ... }
17  var
18    InTime, OutTime, TimeDifference: TDateTime;
19    DiffHours, DiffMinutes: Integer;
20  begin
21    TimeDifference := OutTime - InTime;
22    {ShowMessage(DateTimeToStr(TimeDifference);}
23    DiffHours := trunc(TimeDifference * 24);
24    { DiffMinutes := trunc((TimeDifference * 24 * 60) - (Trunc(TimeDifference * 24) * 
25  60))}
26    DiffMinutes := trunc((TimeDifference * 24 * 60) - (DiffHours * 60))
27  end;