Although Amtrak tries to contact everyone who is affected by a schedule change, foul-ups happen. Amtrak is constantly tweaking schedules, so next June's California Zephyr may well run at different time than now.
Just to be sure, I would go to the Amtrak web site a week or so ahead of your trip. Do not look at the “Printable Schedules.” Instead, go to the reservations area and start the booking process for the trip you are taking. Enter you origin city, your destination, and your date and time of departure. The display showing the trains and times is from the current Amtrak reservation system and will give you the up-to-date time for your train. Or, you could go the low-tech route and call Amtrak and ask.