I was trying to explain to a friend of mine why my compass watch had to be calibrated to work correctly in Southern California. I realized as I was explaining that I had forgotten everything the Boy Scouts taught me (well, I technically never made it past Webelo).
Go forth onto Google!!! Found a couple of neat entries on True North, and Magnetic Declination, but the best part was finding this cool animated gif:
The image depicts the change in the Earth's Magnetic Field Declination from 1590 to 1990. It should be noted that at the time of WWII, there was a -10 line sweeping quickly through Europe... (Random correlation, or cause/effect? YOU decide!) ;-P
Oh wait, there was something else that's almost cooler than that image above. True North Snacks!! Mmmmmmm, snacks!