My company used to have casual dress on Fridays only. Recently they issued a policy change stating that everyday would be casual. Of course they listed some specific guidelines, such as no men's shorts, no women's tank tops, men's shirts had to have a collar, no men's sandals, etc.

The next morning, even though already at work, I emailed my boss and copied our team: "Sorry, running a little late today- didn't realize how difficult it would be finding women's sandals that fit comfortably."