Before you go any further I would look at that key field. I do not think the date is going to be unique for an identifier. If you have two sets of scheduled tasks on the same day it is going to create an issue with that key field.
It sounds like you need a task assignment table which is a many to many (join) relationship between your tasks and your assignees (whatever you are calling them, maybe resources or employees, etc.)
That allows the multiple assignments.
I personally, in most business cases, do not like multiple assignees in tasks as it could lead to "I thought the other person had it" But that is just me and some people on my team dont like that. But since I develop QB for our team I get the last say :)
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Ivan Weiss
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