on my android, an HTC, i use Business Calendar and then use the google system to link to TB Calendar on the floptop, this works really well, however, would be great to be able to bypass the need for Google cal link and drop Business Cal to have everything under TB (just as i did for email, stopped using AquaMail in favour oif TB!)
We understand that user desire for a Thunderbird branded calendar is strong. However there are compelling time sensitive, important feature improvements and technical debt which must take priority before considering a project as large as a new calendar.