...
Within a Smart Client the user can manually override the Locale Settings as well through the Smart Client preferences.
For more information on Localization, see SA-JH-Internationalization and Localization.
The default locale for clients
...
When true, the clients time zone will be used to convert to the server/database time zone. It is highly recommended to use true as the default to always see the correct/same dates/times in all clients (regardless of their timezone). For more information, see Working with Timezones.