Can an entity in an entity-relationship diagram have more than one relationship?
It means that time is an essential component of the relationship.  It's telling you that there's a functional dependency (employee, time) -&gt; project.

In an entity-relationship diagram, I might model it like so:



I made it a weak entity dependent on Employee and with time as a weak key, but it's still a relationship between Employee and Project, hence a weak associative entity.