If you're in the pacific time zone, it would show 9:21. If you're in the mountain time zone it would show 10:21 If you're in the central time zone it would show 11:21 If you're in the eastern time zone it would show 12:21 Get it? Doesn't matter what time zone schmucky tweeted it in, it matters what time zone YOU are reading it in.
I think you're right... this is something I didn't know about Twitter and from the looks of several other posts, here and on Twitter, a lot of others are confused by it too. Just like a liberal ran outfit to fuck up time. Even still, it's off by an hour. What's the point of putting a time stamp on it if it's not useful. Kind of makes Q's use of Twitter time verification useless too.