Element Input Value - Special Purpose - Earned Date

Summary:

What effect does specifying a Special Purpose of Earned Date have on an element input value?

Content (required):

When adding an element input value, one of the Special Purpose values you can specify is "Earned Date.

I'm adding input values to:

• allow users to enter a date worked that is different from the element effective date
• output the actual date earned used in the calculation as a run result (which can be different from the date worked input)

So I'm kind of wondering whether this Special Purpose would help in any way, or whether it is for something specific entirely unrelated. I've done some testing and it doesn't have any obvious effect, but there seems to be no mention of it in the documentation as far as I can tell (like several of the Special Purpose values tbh).