Pretty self-explanatory title. I feel rather dumb asking this since there are answers out on different forums, I just can't figure out how to make it all work in my game.

Currently I'm in Sunset Valley, it is Wednesday in Summer, the 4th day according to Tempest. So, by default the Leisure day is on Thursday, I'm trying to set it for Saturday. Every time I think I may have the correct value, the red holiday circle just disappears on me. I have managed to set it on pretty much any day of the week except for the weekend.

My season length is 7, by the way. Don't know if that's relevant

I don't think this will work on weekend days, also the season change needs 2 days transition, if I remember right.

And when you change the holidays, it will only apply to the next season. But let's wait for other insides.

I don't recall having problems with weekends vs. weekdays, but I agree there might be an issue with a holiday being on the last day of a season. Also we can't always really tell if we were successful in making such a change until the morning (6am sim time?) of the day arrives. The red circle for planning ahead may not always be accurate when a change is pending.