Don’t worry – the world will definitely NOT end on 21st December, despite all the hoo-ha and hysteria in different parts of the world. You can be certain of that!
HOWEVER, all Christians ought to be aware that Jesus Christ has promised to return and forcibly snatch us away [‘rapture’ us] at some time, as described in 1 Thess 4:13-18. The day of His return for us may happen at any time, and is known ONLY to God the Father.
So no-one should be in the least worried about doomsday theories, UNLESS they haven’t repented and believed in God’s salvation as a result of His Son’s sacrifice on the cross. [Remember that true belief is ongoing and needs to be shown by being ‘worked out’, according to Phil 2:12 and Jesus’ words in John 14:23-24.]
Consequences for those who have neglected or rejected Jesus Christ are eternal, and not pleasant to say the least.
If any non-Christians are reading this please have a look at Acts 2:38-39, then join a group of real Bible-believing Christians. Your future depends on it.