From what I know, most schools in Japan are now Monday-Friday after the Yutori movement a decade or so ago. However I think there are still a few private schools that have school on Saturdays, and either way it's not uncommon for clubs to use the Saturday as a club activity day. Either way Saturday school for the most part was abolished.
In this RP though I'm planning to cut students even more slack. School will be from Monday-Friday. And Wednesday will be a half day, with the latter half being dedicated to self-study and/or club activities. For the most part, that just gives our characters to meet up at school, without the burden of classes and such. Either way it's unlikely we'll actually end up roleplaying an entire week fully, as I'll probably skip a few days here and there.
As for Calendar, I was going off memory, so the calendar is much appreciated xD Just need to combine it with a commercial holiday calendar and I should be set. :P