You can lower the frequency slightly by a parallel capacitor/trimmer. However, near all those 32kHz crystals have an undesirable temperature coefficient such that critical adjustment of frequency is a waste of time.
A real world example is the case of my two clock radios, cheap items but amazingly accurate. One has a green LED display and the other has a red one. With the red one sitting on my nightstand and the green one on top of it, the red one runs faster than the green one at about one second a day. With the green on the bottom, they are almost at the same speed, and don't change much at all from day to day.
The slight temperature difference, with the lower one warming the upper one, is enough to change the frequencies by that much.