Not an embarrassing question at all and it caused us some problems too for support data.
In short, you need to create a new datasource thats does a UNION ALL and creates the fields you need.
There are a few examples out there:
I havnt tried this but it also may help:
You are touching a weak area of Tableau (and likely other visualization products too) as evidenced by a long list of repeated questions and a limited list of limited solutions in FAQ: Open & Close Dates. Even so, I do hope mentioned question & answers & resources & ideas collection helps you find a valuable workaround. I recommend you to read Headcount, when given the Arrival & Departure Dates and method 1 in The Cross Join Collection.