It all depends on the place, some people decide to open some don't its all up to them since they own it, you could try and see if they could give you their squedule so you can see what times and days they are opened.
I bet lots of them will be open. The ones near me like to stay open on nights that drunk people will be more likely to go and get things that they'll regret in the morning. :p
Some will be, some wont. They make their own hours and days which they close. The one near me is open on new years.
You can look up piercing shops near you, call them up, and ask if they are open or not :) Good luck.
