I acquired a Poljot 3105 (which is basically the famous 3133 chronograph watch without the chronograph part) on which the date never changed, so I had a quick look into what might be the problem.
The case was very hard to open, almost like it was glued shut. When I finally managed to get the back off I found what looked like petrified remains of a rubber gasket. The movement is held into the case by two lips that fit into cutouts in the case.
The dial sits very snug on the movement, held in place by two screws on the side.
As can be seen, the date advancing mechanism is a rather complicated affair of wheels within wheels, with the pins advancing the date wheel on a planetary wheel inside an orbital wheel. The planet wheel pins are supposed to touch the date wheel on every third orbit, like so:
On the other 2 orbits the pins are not in alignment so the date isn’t advanced:
Now it seems the last person to put this watch together didn’t bother to check the date function, and oriented the planet wheel in a way that its pins never touched the date wheel. So it was a simple fix.
I had to take the keyless works apart five or six times before I figured out that it’s necessary to press the stem release button while inserting the stem back into the movement, or the keyless levers get out of whack… So here are some pictures of the keyless works.
I didn’t pay attention to the center wheels in the above picture, so they are out of order. The hour wheel should sit below the date orbital wheel.
Note that there’s a ring plate around the date wheel held in place by 3 screws, it has two cutouts for the dial feet holes, so the orientation matters.
Below is a “before” picture. Notice that the minute hand was also put in wrong side up (polished side facing the dial). Whoever put this together was an idiot. They also left some scratches on the dial…
