Ok, I know, it would be better staying much longer...
But if it is not possible ...
We are only interested in the fort (of course with jain temple) and in a couple of haveli.
Not interested in sand dunes (for good personal reasons).
We could arrive in Jaisalmer at 1 PM of one day (starting from Jodhpur at 8 AM) and leave at 1PM the following day.
I know: very short time of visit, as in January the daylight time is scarce.
I know: zero time to relax.
But just in case: is fort + a couple of haveli doable in a 24 hours staying?