Strangely enough, ISO 8601 provides that Monday is the first day of the week and therefore Tuesday is the second day of the week. This is counter to the US, as most things are, where Sunday is the first day of the week.
This comes from Tewesday, meaning the day of Tiw, or Tyr, the god of single combat. I never knew of such a thing. Tiw also refers to Mars, which explains the mars lander.
So, now we can slide into Wednesday having learned something. To be forgotten by tomorrow.