Are the days of the week always written in lower case?

In Spanish, the days of the week are usually written in lower case, except if they are used at the beginning of a sentence or if they are part of a proper noun, such as "Lunes Santo (Holy Monday)."

For example:

• Voy al cine el lunes.

(I'm going to the movie on Monday.)

• El martes es mi día libre.

(Tuesday is my day off.)

• El miércoles pasado fui al concierto.

(Last Wednesday I went to the concert.)

• El jueves es el día de la reunión.

(Thursday is the day of the meeting.)

• El viernes salimos temprano del trabajo.

(We left work early on Friday.)