I made a public Google Calendar that you can add to your personal calendar, it will automatically convert to you local time zone.
The time is set to the start of the Giantbomb live streams which begins 30 minutes before the conferences. (The PC Gaming Show, Limited Run Games and Devolver Digital will not have a GB live stream and the time is set to the start of the presentation itself, I don't know about EA Play but it's in there.)
Google Calendar doesn't allow me to export notifications, but you can add that quickly yourself by clicking on each event or by going to the calendar settings and setting standard notifications for all the events.
How to add:
Option 1: Click this link.