That happens to me all the time! I think it happens to me a lot because I work a different schedule every week, and I don't often have the same days off two weeks in a row. If my husband and I are both off and our son doesn't go to babysitter's house at all, I will always swear it feels like a Sunday no matter what day of the week it actually is.
Yep, it happens to me often. If my husband takes a day off of work, I always think the day before that is Friday, since we have something to do as a family the next day, which in my head is usually Saturday....and it messes me up for days!