I use Ubuntu 18.04. I have added a couple of events to the calendar and added 1 day before notification to it. I have set the calendar to launch at the startup. Neither on the same day or the day before, I got no notifications for the set reminders. I haven't added any online calendars to it, using whatever came with stock Ubuntu 18.04.

I reported this first at Gnome Gitlab and was told to ask on distro platform. You can see my thread there below

https://gitlab.gnome.org/GNOME/gnome...dar/issues/459

It will be great to have a fix for it. Thanks.