Hacer San Lunes, “to keep Saint Monday,” meant not going to work on Monday. A study in the journal Estudios de Historia Moderna y Contemporánea de México describes the “tradicional San Lunes, que culturalmente había sido el descanso de facto en ciertos oficios y en sectores populares” (traditional Saint Monday, which had been the de facto day of rest in certain trades and among the working classes).
In 1902, when Sunday rest was being regulated, the newspaper El Faro hoped that “descansando sin emborracharse, el pueblo dejará de hacer San Lunes” (resting without getting drunk, the people will stop keeping Saint Monday).