Quote
testcase
"I can't tell the time on that"
Same here.

If I had to guess, I would say that the red triangle points to the time (24-hour) on the next-to-last outer dial. And that the month dial rotates with the triangle, but slower, so that the red triangle moves from month to month as appropriate.
My only beef is that all nine (yes, nine!) planets are not included, but since the missing ones have 80+ year orbital periods, I can let it slide