OK. The formula for OnTime was faulty! Right one must be
Code:
=IF(AND([Delivered]=0,[DueDate]>TODAY()),"",AND([Delivered]>0,[Delivered]<=[DueDate]))
I.e. when:
1. Document is not delivered and due date is in future, then it is not late jet and OnTime field will be empty;
2. Document is not delivered and due date is today or earlier, then it is late or it is being late when not delivered immediately;
3. Document is delivered, and due date was later or equal than delivery date, then delivery was on time;
4. Document is delivered, but due date was earlier than delivery date, then delivery was late.