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System Information

How do I get a time zone specific time? by Glenn9999
Posted: 1 May 20

I happened to run into a case where I needed to do something that was dependent on the specific time in a specific time zone. Now something like this might be standard function in newer Delphis, but it didn't appear in either Delphi 3 or Turbo Delphi 2006. I ended up coming up with this to do the job: A "Now" function that will give me a time-zone dependent response. It may have issues, but for what I used it for, it seems to be working consistently.


function NowTZ(Bias: Integer): TDateTime;
// make a Now function that works on time zone.
// "Bias" is a UTC "minus" value.  For example, CST is -6, EST is -5.
  TZ: TTimeZoneInformation;
  UTCTime, LocalTime: TSystemTime;
  TZ.Bias := 0;

// set time zone biases for daylight savings time.  This works for most of the US.
// DST ends at First Sunday in November at 2am
  TZ.StandardBias:= Abs(Bias*60);
  TZ.StandardDate.wYear:= 0;
  TZ.StandardDate.wMonth:= 11; // November
  TZ.StandardDate.wDay:= 1; // First
  TZ.StandardDate.wDayOfWeek:= 0; // Sunday
  TZ.StandardDate.wHour:= 2;
  TZ.StandardDate.wMinute:= 0;
  TZ.StandardDate.wSecond:= 0;
  TZ.StandardDate.wMilliseconds:= 0;

  // DST starts at Second Sunday in March at 2am
  TZ.DaylightBias:= Abs((Bias+1)*60);
  TZ.DaylightDate.wYear:= 0;
  TZ.DaylightDate.wMonth:= 3; // March
  TZ.DaylightDate.wDay:= 2; // Second
  TZ.DaylightDate.wDayOfWeek:= 0; // Sunday
  TZ.DaylightDate.wHour:= 2;
  TZ.DaylightDate.wMinute:= 0;
  TZ.DaylightDate.wSecond:= 0;
  TZ.DaylightDate.wMilliseconds:= 0;

  SystemTimeToTzSpecificLocalTime(@TZ, UTCTime, LocalTime);
  Result := SystemTimeToDateTime(LocalTime);

Calling it is very simple...if I want to know what the time is in the Eastern Time Zone:


NowBias := NowTZ(-5); 

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