How could my iPod Touch 4th Generation automatically update its clock when moving between time zones and not connecting to any Wi-Fi networks?
I get the pop up message that Bluetooth can improve location acuracy or something like that; maybe you turned on Bluetooth somewhere in that time frame.

Also, referncing the fact that Google maps, and Tetsujin's comments below, Google maps seems to use something that acts like GPS, to tell me where I am while I have wifi turned off. So maybe a you connected using wifi of some sort to a satellite or something else to help your device locate its self. 

Really interesting situation.