well, you could start with rating the weekdays and produce a formular for that. It would be possible. Wednesday being 100%, Saturday 25 and Sunday 35. If you are on central European time, that is.
It is very difficult to calculate the holidays in an international envionment.... because the photos might be subject to double feedback.
Meaning... you might have a collection of easter pictures that sell better than other pictures at easter time, or you might have area or culture specific images that are not influenced by holidays in other areas.
In short: if you are based in China and mostly sell your images in China, bank holiday will not have much impact.