I used to work for Verizon wireless, all major holidays are considered off peak. (I'm trying to think the holidays always correlated with the days I got a paid holiday )
This includes X-Mas, New Years, Thanksgiving, and a couple others. They didn't do easter, but that didn't matter since easter was always on a sunday anyway.
FYI, for those with a camera phone through verizon wireless most people can access the express network (the high speed internet access) for free if they have the mobile office kit $69.99. Right now there is a snafu in their system. You see the camera phones use the high speed access to send, receive pictures thus customers have it enabled on their account by default. The system doesn't know the difference between sending a picture and using the phone to browse while connected to a laptop it just uses minutes. I believe actually adding this option costs 70 bucks a month so its a nice bit of savings. Its similar to the mobile to mobile on the family share plan, in most billing areas a customer had unlimited mobile to mobile to all VZW customers even though their plan said it was only to those on your family share. These are just errors that are not worth fixing as vzw is too busy trying to consolodate all of the companies it has bought out into two major databases and this will take a good bit of time. Even if they did fix the problem they might have to do it again after conversion.
EDIT: Thanksgiving, X-MAS, New Years, Labor Day, July 4th, Memorial Day
Happy Holidays