I missed GA despite being logged on several times during the setup phase. There is no in-game visual cue (i hear badges appeared, but I didn't notice any). There was no countdown timer like on TW/TB. The out-of-game calendar was changed with short notice and was not visible (edited entry as opposed to new thread).
I hear a lot of people missing it. In my case I was actively looking for it and still somehow missed all the announcements. QoL Suggestion: in-game notification dot on the table (like events, store, guild tables) and a two day countdown timer before event signup starts (like TB/TW).
If same thing happened to you, you can Me Too this bug report