Would someone please explain The Shining to me?

oh yeah, and the cartoon before the film was great - we really need to bring back shorts before features in all cinemas

Last night I joined hundreds of New Yorkers to sit on the grass in Bryant Park and watch a film, the last of their Summer Series.  Now I've seen The Shining twice and I thought this time I might understand it better but no - once again I was left at the end with a feeling of "Oooh.......wait, what?"  Why has Jack Nicholson [SPOILER ALERT] been in the hotel since the 1920s?  That doesn't even make any sense, does it?  It's one of those twists that makes you go "wow!" until you actually start thinking about it.  Despite the fact that I'm not sure I really get why there's a 1920s party going on or why there's someone in a squirrel mask or why a hotel in Colorado employs so many English people or what the hell Tony actually is - I thoroughly enjoyed the film last night, especially getting to watch it outside with a whole lot (and I mean LOT) of other people.  Highlights included:

• the first long shot of Danny riding his tricycle around the hotel with the sound of wheels on wood, wheels on rug, wheels on wood, wheels on rug as he rode without abandon across expensive carpeting (all of those shots are brilliant, but that one stood out)
• the explosion of laughter from the audience as Winifred runs up the stairs, arms akimbo
• the scary scene where the twin girls show up in the hallway that was disrupted by a man standing in front of the screen casually trying to figure out where he had been sitting
• the beautiful breathtaking symmetrical cinematography throughout the film

On another note, if anyone hasn't seen the Shining 'happy trailer', you should watch this now: https://www.youtube.com/watch?v=Os6raCCmAFk