It starts later as CK2 ends later.
I know why they're doing it, I just think it's a shame that they are. My personal opinion is that EU games are more fun than CK, and personally I'd prefer an extra 50-100 years on EUIV with a bit of an overlap than a save game converter (If Johan does convince his coders to make one!) for CK2 with a seamless date overlap.
As I say, I find 1356-1444 more fun in EU than CK, but that's just my opinion, and I'm obvious in the minority or they'd have done it differently (Or they're going to push it back with DLC later). Regardless, for those like me there will be mods for it soon enough I expect!