GFork

Takes the date/time when you last wrangled, and turns it into a message of "X days ago", so you don't have to do the math.
The calculation rounds to the closest full day: if you wrangled 5 hours ago, it'll show 0 days. If you wrangled 18 hours ago, it's already showing as 1 day ago.

The "X days ago" message has a tooltip where it'll show the date/time that Ao3 provided, because the script also removes the usual text above the table of assigned fandoms.

Once you've hit 10 days, the highlight goes from gray to red, to alert you that you're coming close to the allowed 2-week maximum.

PS: Timezones are a mess. If you notice anything wonky with the day calculation, let me know. Your selected timezone might be unrecognized because it's missing off the list in the script, then the scripts treats it as UTC.

Known Issues: If you're running a script that tries to write into the "Fandoms assigned to you..." paragraph at its beginning, this script might inadvertently remove what the other script added. Try commenting out (adding two forward slashes //) code lines #24 through #27. If your other script adds stuff to that paragraph at its end, it isn't affected.