I use the GCal smartapp. Support is withdrawn, but it still works. This SmartApp connects with your Google calendar and can set the equivalent of contact sensors you can use to trigger Core actions or set variables.
You could simply have it trigger on any holiday and set a global variable. In my case, I have GCal triggers for different holidays, birthdays, anniversaries, sports teams, etc… These set a variable and then I have a piston for my outdoor lights that sets colors based on the the variable value. I haven’t had a failure yet so it seems pretty resilient.