Whauboajaiqu50 For the ZRH Airport - Berne itinerary, your regular point-to-point ticket would be valid on the entire day of travel for any train, regardless if earlier or later. The same applies for a Saver Day pass (not refundable), in case such a pass would be offered cheaper than the regular ticket for that day. Try to have a closer look at the respective ticket details before buying, the validity period should usually be mentioned there already.
Just stay away from Supersaver tickets (if available), as those are tied to the specific train and are also not refundable… bad idea if your flight gets delayed!