Or,
Click on your User Name at the Top right, Preferences, Content Options, Disable Holiday Styling.
To OP,
Holiday themes are used for most Holidays, some are better than others ... its a great option to have available to the individual, some like them, others don't. Most sites don't have that option.
I didn't even know that they were on till your post ... I turned them off previously, I had to turn them ON to check it out.
Its a Fun thing, everyone has thier option to have them or not, no need to Dis the website ...
For most people, this place is "Home" ......
Relax a bit, look around and get to know the site and those on it and you'll find its well worth the stop.