How the rotation week is calculated
Schools on a two-week or multi-week timetable need a simple answer: which rotation week is this? The calculator counts full school weeks from an anchor week you define.
Pick the Monday or Sunday that starts each school week. Find the week that contains your anchor date and note which rotation label applied that week (for example Week A). For any target date, find its week start and count how many school weeks lie between the anchor week start and the target week start.
Rotation index = (anchor week index + weeks counted) mod cycle length
If you choose pause during holidays, weeks whose start date falls inside a paused range do not advance the count. If you choose advance, every school week increments the cycle even across breaks.
The embed uses the same math from URL parameters, so schools can host a live indicator without a backend.