Excerpt from the article (it's a long one so maybe take your time to read it, but it is rather interesting):

Teddy Ostrow: Another element of the tentative agreements that may be representative of a greater shift in the union is that the contracts, if they’re ratified, will now expire on May 1st or the day before, which is the international holiday of May Day.

And one could say this is perhaps symbolic, but it also is quite strategic, I think. UAW President Shawn Fain has called on other unions to basically line their own contracts up to expire on that day as well. Can you give us a very brief crash course on the importance of May Day, basically so you can help us understand why the union did this, and what it says about the kind of unionism the UAW is trying to influence across the labor movement?

Barry Eidlin: Yeah, I mean, there are practical considerations, just that having the contract expire at the end of April means that workers are on the picket lines in the spring and summer instead of in the wintertime, which is non trivial when you’re talking about a protracted strike situation.

But it’s really the symbolism that’s important here. And I don’t mean symbolic in the sense of meaningless. I mean symbolic in the sense that it means something really important. So May Day obviously is the international workers’ holiday. Some people sort of say that it’s the real Labor Day and that the one in September is the fake Labor Day, but I think we should just have two Labor Days and we should fight for more Labor Days, as far as I’m concerned.

But May 1st is considered this worker’s holiday. It is to honor the martyrs of the Haymarket massacre on May 4th, 1886. I’m not quite sure what the history is of why it shifted from May 4th to May 1st, maybe it has to do with the Pagan holidays of May Day in Europe, I’m not quite sure.

But in any case. In 1887, some members of the Socialist International decided that they were going to designate May 1st as a workers’ holiday, and it sort of held that position ever since. And there’s been efforts in the U.S. to sort of recapture May Day, even though it originated in the U.S. has never really been as big of a holiday that it is in other parts of the world. So there have been efforts recently to recapture that.

But what’s important here with the UAW aligning their contracts to expire on April 30th, with the strike beyond May 1st and inviting other unions to do the same, to align their contracts, it really speaks to Shawn Fain and the new UAW administration’s commitment to a more class struggle vision of unionism, right? That’s really the story of the UAW contract campaign and the Stand-Up-Strike that ensued, is one of developing a much more explicit framework of class warfare, and that we are fighting not just for auto workers, but for the entire working class, that we are engaged in a class struggle with our billionaire class enemies, drawing these clear dividing lines and mobilizing workers around this broader vision.

And so aligning the contracts to expire the day before May Day and then inviting others to do so is a concrete embodiment of that broader vision, right? It sort of is a way to turn that vision into reality because it creates the structural preconditions for having a mass strike on May 1st of 2028 in a way that is, I mean, you will often hear small groups on the left talk about calling for a general strike and it’s sort of in the realm of fantasy, this actually brings that into the realm of a very real possibility, especially if we see other other unions follow suit.