Dry Erase Calendar Board

Someone gave me a calendar with photos of temples all over the world. But there are these weird symbols on some of the dates:

a white circle… Then a half white circle… Then an ALL BLACK CIRCLE!!!!?????

Is this some code about the end of the world?

I am an amateur photographer and I would like to submit photos to calendar companies freelance, can anyone tell me what companies or websites I should check out???
Thanks so much for your help in advance!

I want to make a family calendar and even a calendar of my favorite photos.

Does anyone have any suggestions of how I can easily create an online advent calendar web page (I don’t know how to create web pages) with photos for each day running up to Christmas?

I would like to make a calendar but I am having a hard time finding a way to make them with my own photos and a way to connect it all together.

Thanks for reading.