SmartPascal
ShortDayNames
Variable		 An array of days of the week names, starting 1 = Sunday SysUtils unit
  var ShortDayNames : array[1..7] of string;
  array[1] := 'Sun';
  array[2] := 'Mon';
  array[3] := 'Tue';
  array[4] := 'Wed';
  array[5] := 'Thu';
  array[6] := 'Fri';
  array[7] := 'Sat';
Description
The ShortDayNames variable provides an array of short string names of the days of the week.
 
Since it is an array, you can update the default values (set by the Windows locale), but this is not advised.
Notes
Warning : these values use Sun as the starting value. This is not ISO 8601 compliant. Use with DayOfWeek, which also treats Sunday as the first day of the week.

You are advised to use DayOfTheWeek which is ISO 8601 compliant, using Monday as the start of the week.
Related commands
LongDayNames An array of days of the week names, starting 1 = Sunday
LongMonthNames An array of days of the month names, starting 1 = January
ShortMonthNames An array of days of the month names, starting 1 = Jan
 
Example code : Show the day of the week for Christmas 2002
var
  myDate : TDateTime;
  day    : string;

begin
  myDate := EncodeDate(2002, 12, 31);

  day := ShortDayNames[DayOfWeek(myDate)];

  ShowMessage('Christmas day 2002 is on a '+day);
end;
Show full unit code
   Christmas day 2002 is on a Tue