I personally use 24 hour time, and I try to have my devices set to that, although I'm normally fine with using 12 hour time, and I can switch between the two fairly easily. Kind of like Vouk, I'm pretty certain that I switch between the two without much thought, sometimes. Just because being in the USA made me grow up with 12 hour, though I generally do a quick conversion of 24 to 12 hour anyway.