Comment # 7 on bug 1116498 from Stefan Hundhammer

This is read and written in this code:

https://github.com/yast/yast-country/blob/master/timezone/src/modules/Timezone.rb

AFAICS this serves as the default for timezone selection. The default is read
from the product's control.xml file.

If the language / country definitions suggest a different timezone for the
language (and country?), that one will be used instad. For many countries, this
gives a clear result, because they don't stretch over multiple timezones:

  German  -> CET (UTC+1) 
  Italian -> CET (UTC+1)

but there are others that don't have such a simple 1:1 mapping; English,
Spanish, Russian come to mind.

AFAICS this works as designed, and there are limits what we can do here anyway.