Understanding user preferences
Many of the preferences assigned to the _system user are system wide values. However, some of them have default settings that you can override for individual users. For the following preferences, the _system user value is used only if the current user does not have a specified value:
date_format
tz
lang
items_page
To override the default date_format for a user, you must create a date_format preference for that user. For details, see Setting-or-changing-user-preferences.
In addition, users might be assigned a role. For more information, see User-roles.
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