META-CHALLENGE SOLUTION

Here you go:

THEME: X MARKS THE SPOT / ALPHANUMERICS — if you take all the Xs in all the grids from the past week, in order, and change each one to a letter of the alphabet based on the number that's in its box (i.e. "X" in a box numbered "20" = T, "X" in a box marked "5" = E, etc.), you end up with the phrase

TEMPUS FUGIT (i.e. "time flies")
You can see the Xs in the today's grid are in the boxes numbered "7" (which represents "G", the 7th letter of the alphabet), "9" (which represents "I"), and "20" (which represents "T")—these are, as you can see, the last three letters in the solution phrase, "tempus fugit."

So the mathematical times symbol (i.e. "X") ends up indicating (via ALPHANUMERICS) the letters in a Latin phrase related to time.

(Note: "time flies" are the last words in the Tears for Fears video I posted Saturday. Not that that should've helped you any …)

Fugit-aboutit!

Signed, Rex Parker, King of CrossWorld