Recent versions of Delphi ships with the TStopwatch record which is for time interval measurement. Example usage:
uses
System.Diagnostics;
var
StopWatch: TStopwatch;
ElapsedMillseconds: Int64;
begin
StopWatch := TStopwatch.StartNew;
// do something that requires measurement
ElapsedMillseconds := StopWatch.ElapsedMilliseconds;
end;