Thread:Project:Support desk/Timezone: "Use wiki default" as default

If a new user registers his timezone should be set to "Use wiki default" rather than to "Other (Specify Offset)" (find these settings in Preferences -> Date and Time).

I didn't find any variable for this in Manual:$wgDefaultUserOptions.

With $wgDefaultUserOptions['timecorrection'] = '02:00'; one can only set the offset - but I want to change the default value of the dropdown.

Thanks for any help!