The  calendar is essential for me, as the blog written:

https://blog.sciencenet.cn/home.php?mod=space&uid=331295&do=blog&id=1318809

The search function of thunderbird lightning is not enough, espically for the repeat/ recurring events.

To solve this problem, i have to downgrade the TB to 60.9.1 version to install the reminderfox add-on etc.

The instruction is shown as pictures as follow:

using outlook.com to sync the local .ics and web-calender.