First off, you are sharing the same 3DS. StreetPass is a functionality that is meant to transfer data between two or more 3DS Systems, not the same system. If you share the same 3DS, then you cannot share Streetpass Data.
Second, I have NO clue why your 3DS time isn't changing. Head to the System Settings and try and figure it out yourself. If you have Parental Controls on your 3DS to block it, well tough luck.