I once did a consulting gig for a huge bank and learned that thier international funds transfer network would grind to a crawl each May Day.  All over the world workers would take a day off and capitalism would grind to a halt.

If you work in middle management in any large firm you learn to despise one particular task, organizing a meeting.  Coordinating a diverse group of people to all show up at the same time and place; the more diverse the group the harder it is.

A powerful charismatic actor in a distant part of my organization recently organized a gathering in the early evening.  The attendees all showed up.  It was a wily move, putting our loyalty to the workplace in competition with our loyalty to what ever social network we page in just after the workday ends.  He sweetened the deal with food.

So I have this theory, “which is mine,” that one of the functions of holidays is to create interruptions in the usual dance of social network coordination.  They are society device to relieve the stress that builds up if these secondary social networks don’t get some attention.  This theory leads to a natural question: “what secondary social networks did you nurture during the last break?”

The scarcity of these breaks leads to competition.  Around my house we started joking this last holiday season.  “You know, that the Christians stole this holiday from the pagans.    Right?”  “Oh yeah! …  But then, the Pagans stole it from the Neanderthals.” Of course the the commies stole May Day from the Pagans too.
Modern life makes the war on holidays all that more interesting, since modern life is al about juggling numerous social networks.
We don’t do May day in the US.  The tension between capital and labor played out in different ways.  We do have a holiday assigned to labor, but it’s in September.  I don’t think I’ve heard, even once, somebody complain about how we have lost touch with the true meaning of Labor Day.  Putting our Labor Day on the opposite end of the annual calendar from May Day was presumably a scheme to avoid the US labor movement coordinating it’s activities with thier international brethern.

If your goal is to engineer a social network you spend a lot of your time attempting to orchestrate these points of rendezvous.  In or out of existence depending on your goals.    Eid ul-Fitr is an example of a holiday that is close to, but doesn’t quite, land on the exact same day worldwide.  I’ve read rants from people who feel it ought to.  There was a long standing yearning in my household that, if only, we could all agree to exchange presents a week after Christmas morning, think of the money we could save!
Sometimes you find competing holidays running up right against each other.  Halloween next to All Saint’s day is a classic example.  My favorite it Queen’s day in Holland, right next to May day.