If you've been having trouble using Twitter in the past few hours, you are not alone. The issue seems to be widespread, with the bulk of reports coming from users of the mobile site, and apps like Twitter for Android; we have also verified that some desktop users may be affected as well.
The message you'll be greeted to is “Something is technically wrong. … Thanks for noticing–we’re going to fix it up and have things back to normal soon.” If you're in certain time zones, like Eastern European Time, you will get: "Twitter is currently down for maintenance."
The company has already confirmed on its status blog that they are currently working on solving the problem. One Twitter user is reporting that the servers seem to think it's a problem with dates, with Tweetdeck showing posts backdated by 365 days.
The service still works if you're still signed in, but on some time zones the service it still says it's currently under maintenance. Are you also experiencing issues? Tell us in the comments below.
UPDATE (December 28 9:28 P.M. PST): Twitter has announced on their blog that they have solved the issue.