[Delphi] How do I handle time zones and date/time formatting in Delphi?

In Delphi, you can handle time zones and date/time formatting using the TTimeZone and TDateTimeFormat classes. Here's how you can do it:

  1. To handle time zones, you can use the TTimeZone class. It provides methods to convert between local time and UTC (Coordinated Universal Time) and to retrieve information about time zones.

    • To convert a local date/time to UTC, use the TTimeZone.ToUniversalTime method:

      1var
      2  LocalTime, UniversalTime: TDateTime;
      3  TimeZone: TTimeZone;
      4begin
      5  TimeZone := TTimeZone.Local;
      6  LocalTime := Now;
      7  UniversalTime := TimeZone.ToUniversalTime(LocalTime);
      8end;
      
    • To convert a UTC date/time to local time, use the TTimeZone.ToLocalTime method:

      1var
      2  LocalTime, UniversalTime: TDateTime;
      3  TimeZone: TTimeZone;
      4begin
      5  TimeZone := TTimeZone.Local;
      6  UniversalTime := NowUTC; // Assuming this is a UTC date/time
      7  LocalTime := TimeZone.ToLocalTime(UniversalTime);
      8end;
      
    • You can also retrieve information about a particular time zone using the TTimeZone.FindTimeZone or TTimeZone.GetTimeZone methods:

      1var
      2  TimeZone: TTimeZone;
      3begin
      4  TimeZone := TTimeZone.FindTimeZone('America/New_York');
      5  // Use the time zone...
      6end;
      
  2. To handle date/time formatting, you can use the TDateTimeFormat class. It provides methods to format date/time values according to various patterns.

    • To format a date/time value using a specific pattern, use the TDateTimeFormat.Format method:

      1var
      2  DateTime: TDateTime;
      3  FormattedDateTime: string;
      4begin
      5  DateTime := Now;
      6  FormattedDateTime := TDateTimeFormat.Format('dd/MM/yyyy HH:mm:ss', DateTime);
      7end;
      
    • You can also use the predefined format settings provided by the TFormatSettings record. These settings include properties like ShortDateFormat, LongTimeFormat, etc. For example:

       1var
       2  DateTime: TDateTime;
       3  FormattedDateTime: string;
       4  FormatSettings: TFormatSettings;
       5begin
       6  DateTime := Now;
       7  FormatSettings := TFormatSettings.Create;
       8  FormatSettings.ShortDateFormat := 'dd/MM/yyyy';
       9  FormatSettings.LongTimeFormat := 'HH:mm:ss';
      10  FormattedDateTime := DateTimeToStr(DateTime, FormatSettings);
      11end;
      
    • Additionally, you can use the TDateTimePicker control to allow users to select and display date/time values in a specific format:

      1var
      2  DateTimePicker: TDateTimePicker;
      3begin
      4  DateTimePicker := TDateTimePicker.Create(Self);
      5  DateTimePicker.Format := 'dd/MM/yyyy HH:mm:ss';
      6  // Use the DateTimePicker control...
      7end;
      

These are some ways to handle time zones and date/time formatting in Delphi. Choose the approach that best fits your requirements and application.