Definitions

THe festivity is the anniversary of the Mexican Revolution,
it is on November 20th.

The holiday moves to the previous Monday to avoid creating
a "bridge" / puente, which is when you have a Monday or a
Friday between the holiday and everybody will take that day
off.

So today November 17th is the Mexican Revolution Anniversary Observed !!

Well, they observe it today so that a long holiday weekend can be enjoyed to stimulate tourism, but it will also be observed on the 20th because the teachers use any excuse to miss class, and then since there won't be any school Thursday they'll take Friday off just for the heck of it and create another unofficial long holiday weekend. The lack of professionalism and seriousness by our teachers is a huge factor in too many of our problems, especially here in Guerrero as well as Oaxaca and Chiapas.