From what I know, a few days if you get lots of sleep. Try taking it off and putting it on again…? XP[/quote]
Splints run an extremely-long-odds check every so often to see if the limb they’re on goes to 1 HP. (At that point, the splint’s done its job, OK to remove it, and you heal as normal.) At base, it’s supposed to take about 14 days of constant wear before you can expect the check to come through, so a whole season under default season-length.
You can hinder your odds (takes longer) by having a drug addiction, including alcohol/nicotine.
You can help your odds (heals quicker) by being Healthy (vitamins, etc), Full, Slaked, having faster-healing traits, and laying down (the “Sleep” command, even if you don’t actually sleep).