Is there a way to change display based off sunrise/sunset?

Want to change the background whether it is daytime or nighttime out. Is there a way to pull that info in or do I need to just guestimate a static time switch over?

I cant see a tag for expression that could be used for this. Yet there is a complication short text, that can be set to display time of coming sunset or sunrise that changes to the next event when ever the time passes. Maybe this could be used as sloppy workaround, if you are not going to use the watch face in polar areas where both events can occur close to noon, but I am not sure how it would show on real watch.
In the preview it shows the time always in 24h mode with leading zero. So I managed to insert night image as bitmap font for digit 0 which shows after sunset and day image for digits 1 and 2 which eventually show after sunrise. To cover full background area with bitmap size 450px the text field has to be aligned to left and bigger than 450 to show just the first digit.
It would be much easier and more universal, if the default icon could be replaced with custom images, but I don’t know whether or how could that be done.