The calendar features a person waving the International Cooperative Alliance flag. In their right hand, they are holding a piece of paper that says "COOP". The rainbow flag was adopted by the ICA in 1925. According to Wikipedia, it symbolizes unity in diversity and the power of light, enlightenment, and progress.

Below the year, it says "ONE FOR ALL AND ALL FOR ONE".

I saw the image from twitter user sovietvisuals (nitter link)