many people think of tuesday as the third day of the week but according to international standard ISO, it is the second day of the week!
So according to the International standard ISO, they week starts on Monday?
yes. also the name tuesday derives from the old english "tiwesdæg" and that means "tiw's day"
Do all the names of the days of the week derive from old english?
im not sure about other days  but youre probably wondering what tiw is, tiws day was the day of tiw or tyr. tiw is the god of single combat, victory and heoric glory in norse mythology.