Hello kurtw
Please contact SBB: +41 51 225 78 56 (24/7, waiting times may occur), or write SBB using this contact form (keep in mind that a reply may take multiple days):
https://www.sbb.ch/en/help-and-contact/customer-service/praise-comments.html
We do see this error from time to time; it concerns people living in another time zone than Switzerland, and mostly for peole having the time synchronisation of their device set to manual instead of automatic.
You may want purchasing tickets using the SBB Mobile app. The issue does not exist there, whatsoever.
We will notify SBB once more about this misbehaviour of the web shop.
Kind regards,
Roland