The whole "casual Friday" thing that has metamorphisized into casual everyday is now a custom in a lot of countries.
This phenomenon started in the Silicon Valley back when the computer industry was in it's infancy. Hewlitt Packard asked their employees to come in on Fridays wearing casual work clothes so that everyone could pitch in and help in the shipping department. Friday was the main shipping day and in order to get the orders out they needed everyone's help.
Now it's everywhere. If you wear a suit any day of the week in the Silicon Valley you are picked up and driven to the border and sent on your way with a stern warning.
Michael