This particular one doesn't know which date it is – except through the advance of time (i.e. hours, mins, secs). It seems the date display starts advancing by 1 at 8 p.m., a process that is finished at 2 a.m.
If a month has less than 31 days, necessary adjustments must be made manually (pic1 from Portugieser manual).
But there are other IWC watches which do have a "calendar driving wheel" tracking days, months and moon.
Great to see the vessel "unplugged" (if that's what it was). Hope you wouldn't need no "device" installed. Kek!
Take it easy with the clockwork and getting back to "normal" though. Having a Saturday beer right now to your recovery. Cheers!