Yeah... They work their tails off.. I feel bad for them. Maybe it was the 22nd and they moved it or something. It's still a Monday this time though so that rules out a bunch of people with regular day jobs going. Unless it's a holiday.. I forgot.. I think there's a holiday in there somewhere..
The reason every Sunday is in red is because that's the Christian Sabbath, a day off. Other dates in red will also be days off. This is how it's been done with calendars for a long time. Other entities honor Sunday as a day off, as well. One example that pops into mind is the Japanese school system; full days Monday-Friday, a half-day Saturday, and Sunday is a day of rest. Also, the holiday view for that linked calendar shows only 1 Sunday holiday for the US--Daylight Savings time.
I'm sure that if you used every nation and creed's calendar you could get a holiday for every day of the week, but that's not what you put up.