Week numbers are… confusing, to say at the least. There’s no instinctive connection (well, for me) between a date and the corresponding week number.
To make matters worse, there are multiple ways of numbering weeks. There’s the ISO-standard way, the way used in northern America, and another way that’s apparently used in the middle east (see Wikipedia).
So, just for the hell of it, I made a “handy” page that tells you if the ISO and US numbering systems are numbering the weeks the same way this year.