Same as with the months, the short and long day names can be set using these two variables. The following example shows how you would change the variables to contain day names in Spanish:

SET DayNames = 'Lun;Mar;Mie;Jue;Vie;Sab;Dom';
SET LongDayNames='Lunes;Martes;Miercoes;Jueves;Viernes;Sabado;Domingo';

As these variables replace the regional setting in the operating systems when the application is published, a person in Germany will still see names in Spanish, as set in my example.

To dynamically change these, you either need one application per regional setting which is not recommended, or you can dynamically format names and dates in the front-end by using expressions.