Week programme on a Vents unit

The unit runs its own weekly schedule, and it keeps exactly four intervals a day — each with a fan speed and a target temperature. They can be changed, but not added to or removed: an interval you do not want is one you shorten to nothing. An interval stores only when it ENDS; the next one begins there, so moving one end moves every start after it. Days are written one at a time and read back, so a day the unit did not accept is reported rather than assumed.