One solution would be to draw the clock flipped over the x axis and mirror your surface back before the flip. This will make the top be rock steady but the ends will now be jerky. You could definitely make both ends smooth but you would have to simulate the drawing of the arc through a series of lines. This will give you some more problems due to the lack of sub pixel support. You could use aaline for sub pixel support but you would have to be mean to the processor to get a nice filled in arc. Drawing might be better achieved through another library. pycairo looks very promising.
I wrote a small clock program that I might use if it turns out well, but
I am having a small issue where the top of the arcs that grow over time
shifts when I would like it to stay still. Does anyone know how to
achieve this?