Let me pose an idea: The precission of the clock is coming via the arduino (that has it's own clock -quartz one), so the DC motor (or steeper or any type that can be minimally feedback controlled) has just to (slowly) correct the position of the hands along -say- the following hour (you need a "1 hour lapse" sensor in the clock itself). Such a case, you increment(decerement) a little bit the speed every hour to adjust it to the "real time" (arduino one).
¿Is it feasible?