Actually, it was yesterday. But I wrote about it on Cinco De Mayo:
As an example, one of the other public holidays this month is May 18, the Dia de la Expropriacion Petrolera—the anniversary of the Nationalization of the Petroleum Industry in 1938.
This was the biggest armed robbery of the twentieth century. It left all the oil in Mexico in the hands of corrupt Mexican governments, who couldn't even get most of it out of the ground; a lot of it is just sitting there, because they won't allow foreigners to touch it. And this is a public holiday?