Problem - I have an application that items needs to keep the original time of where it was entered.  This information is saved in XML and when you call XMLTimeToDateTime it auto adjusts the time.  For example 11:00am entered on eastern time is 9:00am mountain time.  Daylight savings also has the same issue when the time changes.

I didn't find any simple clean solutions online, so I am posting this for any others that have this problem.

Solution to adjust the time.  UTC format adds a Bias time on to the end of the time format.  So all you need to do is get the Bias for the time coming in and the Bias for the current computer and then adjust the time after calling XMLTimeToDateTime.

Code - Hopefully I didn't forget anything in stripping this out.

Uses
  XSBuiltIns, IdGlobalProtocols, DateUtils, Windows;

procedure TDateInput.SetDateXml(const Value: String);
var
  curAdj     : Integer;
  adjDiff    : Integer;
  XSDateTime : TXSDateTime;
  tz         : TTimeZoneInformation;

begin

  adjDiff := 0
  if value <> '' then
  begin
    XSDateTime := TXSDateTime.Create;
    try
      XSDateTime.XSToNative(Value);
      adjDiff := XSDateTime.HourOffset;

      case getTimeZoneInformation(tz) of
        TIME_ZONE_ID_STANDARD: curAdj := -(tz.StandardBias + tz.Bias) div 60;
        TIME_ZONE_ID_DAYLIGHT: curAdj := -(tz.DaylightBias + tz.Bias) div 60;
      else
        curAdj := -(tz.Bias div 60);
      end;
         
      adjDiff := adjDiff - curAdj;

    finally
      XSDateTime.Free;
    end;
  end;

 

  Self.fDate := XMLTimeToDateTime(value);
  fDate := IncHour(fDate, adjDiff);
end;