First let me point out the real error in the sentences above – you must put a comma after 2003, no matter what.
Restrictive clause – provides information essential to the meaning of the sentence
Non-restrictive clause – provides information, but if removed, would not change the meaning of the sentence
There are those who say that that should only be used for restrictive clauses and that which should only be used for non-restrictive clauses.
There are those who say you could use either, so long as you set off non-restrictive clauses with a comma.
In this case, your adjectival clause is a non-restrictive clause – in other words, when you remove the clause, it doesn’t change the meaning of the sentence. Going by the first rule (which I prefer), you should use which.