This past Saturday and Sunday in China were work days while Monday-Wednesday are public holidays for the Dragon Boat Festival.
In February I had no hope of getting in to the Natural History Museum in London because of school half-terms.
Last fall my Rio de Janeiro plans had to be changed because certain areas of Brazil celebrate Black Consciousness Day (Dia da Consciência Negra) with businesses closed on November 20.
When I arrived in Guyana needing a same-day Suriname visa one July there was a holiday that no public source that I had consulted listed.
I can continue rattling on through religious holidays and local festivals. The point is that web resources such as Wikipedia generally only do well with official public holidays in countries. Local websites can help, for instance China Briefing is my annual China holiday bible, yet those can just as easily be incomplete or out of date.
So for time-sensitive plans I have no suggestion other than old-fashioned pick up the phone or email legwork contracting locals you know, your hotel, etc. to avoid empty streets and locked doors. The flip side is you might stumble into some fun festival.
Readers, have I missed any great holiday resource? What are your unexpected holiday stories?