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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 Internationalization and Localization.
The default locale for clients
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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.