What is the syntax in Freeform SQL to search for a date range?

I'm trying to harness the power of Freeform SQL on the WorldServer, but I can't get the query right.

Is there any documentation available for this?
The only SDL source I've found so far is this post:

This helps, but it only lists some very basic portion of the syntax. I'm looking for something more complete.

To be concrete: How do I search on a date range?
I've tried a lot of variations of this code, but to no avail:

[Created on] > '2020-01-01'

Thanks for any suggestions.