How to teach the days of the week

I won't post a picture of this so you will just have to take my word for it...my children have both learned the calender with a very important teaching tool...days of the week underwear. My daughter became obsessed with hers last year, requiring me to tell her not only what day it was but how to spell it so that she could find the correct pair every morning. My son, who prefers to go commando (I know, TMI) recently informed us that he would wear underpants if he could also have a days of the week pair. Thank you Gymboree, for making them in a boys sports version! I knew their lessons were well-learned the day I overheard Jack say to his sister, as they were writing letters, "Jane, could you pull your skirt up for a second so I can see what day it is?"