Why does my 3DS Activity Log claim I've spent less time playing a game than the game itself?

I've noticed an interesting property of the 3DS Activity Log: it seems to track less time played than the internal play clock for most titles I've tried on the system.

Take a DS game I recently completed, Solatorobo: Red the Hunter, as an example. Its internal system clock claims a play time of 23:09, whereas the 3DS Activity Log claims I've actually played the game for 16:56 (in hh:mm format). Another notable is the DSi title Shantae: Risky's Revenge, which claims I've played for 5:17 (rounded up) despite Activity Log stating that I've actually played for 2:12.

Which of these reports is more correct? My null hypothesis is that the 3DS Activity Log is more trustworthy -- by virtue of not counting suspends against the play tally -- but I have no data other than my vague intuition of how much real world time I spent to back this up. I would be especially interested in learning how the 3DS Activity Log tracks time spent for each title versus the most common methods used in DS and DSi titles.

Thanks for reading.

In my experience the Activity Log is inaccurate for DS and DSi titles when you've suspended them across midnight.

When I first got my 3DS, I noticed it discarding any played time before midnight if I suspended it overnight - I'd play a game for an hour before bed, go to sleep, play an hour the next day, then quit and check the Activity Log, and I'd see a single hour played.

Recently, this hasn't happened, but instead I seem to have the entire day counted as one play session even if I took suspend breaks during the course of the day. I cannot say if this changed one of the firmware updates, or if it's just another symptom of the same underlying bug.

I only recall one game that counted suspend time against the in-game timer, Hotel Dusk, in which I racked up about 150 hours of supposed play time. If Activity Log is accurate, it should always be longer than the in-game reported time. It will count time in save menus, option screens, music players, replays if you give up and come back later at an earlier save point, and so on.

Which is more accurate depends on the kind of game, but in general the in-game time is probably more accurate, especially if you are trying to gauge the length of a game.