We're nearing the summertime slump for game releases (most are released in the other 3/4 of the year), and Sony decided to switch up how they operate their PSN updates. Previously, Sony would consistently update the PS Store on Thursdays.

As of May, Tuesdays have become the new day for PSN updates in North America, and the PSN content in Europe will be updated on Wednesdays. Presumably, the days for which other regions update their PS Stores will remain the same.