When editing a talk that already has attendees booked, changes to the title, date, or time will trigger a new prompt on the confirmation screen. To ensure this appears, please go through the full editing flow and click through to the Speaker tab and hit Save, rather than using Save & Close in the Details tab. That way, you’ll be given the option to send an updated calendar invite to attendees.
Please note that this feature is only available for events set up as an Ongoing Series or a One-Off Workshop, and only if calendar invites haven’t been turned off for the event.