I found this sitting in drafts, short post regarding period overlapping.
With simple logic we can eliminate the OR conditions related to all possible combinations.

The post:

The possible four cases where period overlap can occur are:

One way we can determine the overlapping periods is if we use OR conditions for all cases, e.g.:

If you are familiar with De Morgan’s laws (from school 🙂 ) then:

With this implemented, we can get the following condition: