I had such a hard time to create reminders for calendars which were some time before the calendar thing happens. Both me and my dad put a lot of things into our calendars which we want to get reminded of by home assistant with text to speech. But there seems to be no easy way to set a reminder time other than the exact minute when it happens.
But what I think most of the people need is a reminder earlier like one hour before each happening so you have the time to drive there or 2 minutes before the online meeting so you have the time to start the video conferencing software, etc.
In calendars there is build in a reminder time which you can set arbitrarily to each event but there is no way in HA to get a trigger on that to do something with it. Also just defaults would be ok for all events.
I hacked it with a timer which fires every minute and checks if it should announce something or not but it took me a long time and I know my dad wouldn’t be able to do it himself while I know that this is the main thing he uses with home assistant because I get a call within a couple of hours as soon as it’s broken for any reason.
He wanted that functionality because he doesn’t look at his phone every couple of minutes, and so don’t I, and he missed many appointments with doctors and others before. But with it he gets reminded 90 minutes before the appointment, 30 minutes before and on the occasion of the event. Especially older people would really appreciate being able to set it up like that to be reminded of things in advance.