Black 2 and White 2 are the only Pokemon games I own where the game will still add in game hours when the ds is closed. For example, earlier this morning I turned on my ds and saved my game, as I realized I hadn't done this recently. The time on the game was 19:01 (I was at the Virbank Complex, so this is further evidence of this, I did not spend 20 hours to get to Virbank city.) Couple minutes ago I opened my ds again and attempted to save again, having not played at all in between. Clock said 21:28.
Is this a common known fact? This happens on both copies of this game that I own. I don't have the og BW to test this on.