This thread was talking about it:
https://www.disboards.com/threads/2017-holiday-events-start-11-18-this-year.3630977/
The Hogwarts projection show starts at dusk and repeats every 20 minutes (it's 6 minutes long). Yesterday was the first day, it was CROWDED. Best places to view is by the snowman/frog chior stage, but the bridge works ok too. It did thin out slightly toward close.
Now - Dec 17, the parade starts at 5:30pm (Some places have it listed as 5pm, but it's 5:30!) The best place to view is by the big Christmas tree in the New York section of the park. (Near mummy) From Dec 18th until Jan 6th it's at 8PM. You are going the day before it typically gets extremely crowded, but it will still be packed. I'd get a spot probably 30-45 minutes before the parade starts. It starts by Mel's so it's toward the end of the run, but Santa stops to light up the Christmas tree there in the New York (and thematically it fits better there).
Grinchmas aka "How the Grinch Stole Christmas" show goes on (entrance is next to One Firsh Two Fish) 10:45am, 11:45am, 12:45, 1:45, 3:30, 4:30 and 5:30 and 6:30 For the day you are there, get there at least a half hour before the show starts, it usually fills up.
The other Christmas shows: Frog Choir in Hogsmeade, Celestina Warbeck in Diagon Alley, the Blues Brothers Christmas and Barney Christmas (This one has Frosty the Snowman too) all vary.
Mannheim Steamroller concert is at 7pm at the big stage by Rip Ride Rockit, Dec 17 is the last day of the concert too.
Show times are posted here (Usually, it'll update for later dates as it gets closer)
https://www.universalorlando.com/web/en/us/plan-your-visit/hours-information/show-times/index.html
There's a LOT of Christmas stuff at Universal this year by an order of magnitude more from prior years, it would be hard to do it all in a day. (And that's not even counting regular rides, etc)