@magmar i thank you for the explanation and a quick response
@karsten13 thx !!! for extra info

Made my day !!!

Using de standard calendar module the (symbol: "facebook-f") with (symbolClassName: "fab fa-",) Works great its from "
    font awesome" v5 but using (symbol: " fa-circle-m", symbolClassName: "fa-solid",) doesnt seem to work.
    I'm only looking for Letters to represent the first letter of te person that has to do there tasks on the calendar.

hope you can help me out