The modern days of the week are named from the Romans (Saturns-day, Suns-Day, and Moons-day), and the rest from Norse/Anglo-Saxon gods. Sunday being the first day of the week is primarily a Jewish/Christian preference that never made much since to me because it's God's day of rest, hence the last day. Try again! :D

(Accio is a treasure vault of random useless information, if the game was easy it wouldn't be fun! ;) )