You can set the system default time zone for your system using the DBS Control utility flags SystemTimeZoneHour and SystemTimeZoneMinute. If you are using time zone strings to convert to Daylight Saving Time and back automatically, you might also need to change the setting for the DBS Control flag TimeDateWZControl.
For information on using DBS Control to set the default time zone for your site, see Teradata Vantage™ - Database Utilities, B035-1102.