Post an announcement

Changing the time or the place tells everyone by itself. An announcement is for everything else: where to park, the gate code, which door, bring a jacket. It sits on the event as a board rather than a feed, so the newest one reads in full and the older ones sit under it as single lines you can open.

Post one from the Announcements section on the event. You can edit a post in place afterward, which fixes it without telling anybody twice, and remove one that's no longer true.

Your guests hear about it, and anyone who said Going or Maybe also gets it in their Signals, so it's still findable after the notification is gone. For the one that genuinely can't wait, an announcement can also go out as a text blast, capped at three per event.