Rest between shifts
Rest between shifts is the minimum gap a person must have between finishing one shift and starting the next. It is fixed by law in many places and by the workplace itself everywhere else.
Why it matters in a small workplace
Closing one night and opening the next morning is the easiest mistake to make in a week and the hardest to see: both shifts are reasonable on their own, and only the gap between them is wrong.
How Weeksort handles it
A minimum rest belongs to a rule set, and rule sets are applied to people. Break one while assigning and Weeksort says so, naming the gap it found and the minimum it expected — and it still lets you go ahead, because it warns rather than overrules.