Available Timezones
What are the available timezones in SlickStack for the server itself? Well that depends on Ubuntu itself. The format of the timezone you want is very important, because Ubuntu does not like to use acronyms like GMT or UTC (except, confusingly, for the standard UTC timezone itself).
Change the SS_TIMEZONE variable in ss-config using the following timezone formats on this page:
http://manpages.ubuntu.com/manpages/bionic/man3/DateTime::TimeZone::Catalog.3pm.html