Credit card expiration date changes in Safari as time zone changes

I've noticed for the last year or so, whenever I travel from Eastern time zone (my home) to Central time zone or even Pacific time zone that my credit card expiration date month changes in Safari auto-fill. For example, if the expiration date is supposed to be 09/2017, it will be 08/2017 in both Central and Pacific time zones (it never changes by more than a single month). If I go offline and manually change the time zone, I see the same results as I choose time zones west from Eastern across the U.S.; however, if I change to a European time zone, the correct date remains unchanged. Is there some way to prevent this, or is this just a bug in Safari? [Sierra 10.12.5 on a MacBook Pro (Retina, 15-inch, Mid 2014) using Safari 10.1.1]