[disjunct]

Some school schedules are done so classes meet every-other-day. There are A days and B days, which is specified because certain holidays or exam periods might necessitate a break in the sequence.

Schools are often cute with it; they theme the days with their school colors instead of A/B.

[mdwalters]

Yes, we do this, every time there's a holiday/PA Day, the days are pushed forward, so students won't miss that day.