I looked at the Thunderbird calendar and decided I didn't need it. After that, I could not get rid of the "Today Pane" button on the bottom line and calendar entries in the View menu. An internet search showed many people with this issue, in years past, and no solutions that work today. I finally removed the today pane link by saving my local folders and then clean-installing Thunderbird from scratch with a new profile. I'd like to suggest a "enable/disable" or similar option for the calendar.
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