Use User Settings API to change your general settings on server.
HTTP Request
https://hostname:4083/index.php?act=usersettings
Parameters
| Name | Type | Value | Description | Required | 
|---|---|---|---|---|
| act | GET | usersettings | The action which is specified to carry out specific operation | Yes | 
| editsettings | POST | 1 | If set then the user settings will be edited | Yes | 
| language | POST | language | The language of the panel will be set Eg : polish, english | Yes | 
| skins | POST | skins | This will set the theme for the panel Eg: Currently selected theme will be “default” | Yes theme.Otherwise user can pass name of the custom theme directory under /usr/local/virtualizor/enduser/themes | 
| timezone | POST | timezone | This will set the appropriate time zone for the user. Value will range from -12 to +12 | Yes | 
For selecting the timezone follow the table given below:
| Value | Timezone | 
|---|---|
| -12 | (GMT -12:00) Eniwetok, Kwajalein | 
| -11 | (GMT -11:00) Midway Island, Samoa | 
| -10 | (GMT -10:00) Hawaii | 
| -9 | (GMT -9:00) Alaska | 
| -8 | (GMT -8:00) Pacific Time (US & Canada) | 
| -7 | (GMT -7:00) Mountain Time (US & Canada) | 
| -6 | (GMT -6:00) Central Time (US & Canada), Mexico City | 
| -5 | (GMT -5:00) Eastern Time (US & Canada), Bogota, Lima | 
| -4 | (GMT -4:00) Atlantic Time (Canada), Caracas, La Paz | 
| -3.5 | (GMT -3:30) Newfoundland | 
| -3 | (GMT -3:00) Brazil, Buenos Aires, Georgetown | 
| -2 | (GMT -2:00) Mid-Atlantic | 
| -1 | (GMT -1:00 hour) Azores, Cape Verde Islands | 
| 0 | (GMT) Western Europe Time, London, Lisbon, Casablanca | 
| 1 | (GMT +1:00 hour) Brussels, Copenhagen, Madrid, Paris | 
| 2 | (GMT +2:00) Kaliningrad, South Africa | 
| 3 | (GMT +3:00) Baghdad, Riyadh, Moscow, St. Petersburg | 
| 3.5 | (GMT +3:30) Tehran | 
| 4 | (GMT +4:00) Abu Dhabi, Muscat, Baku, Tbilisi | 
| 4.5 | (GMT +4:30) Kabul | 
| 5 | (GMT +5:00) Ekaterinburg, Islamabad, Karachi, Tashkent | 
| 5.5 | (GMT +5:30) Bombay, Calcutta, Madras, New Delhi | 
| 6 | (GMT +6:00) Almaty, Dhaka, Colombo | 
| 6.5 | (GMT +6:30) Yangon, Myanmar | 
| 7 | (GMT +7:00) Bangkok, Hanoi, Jakarta | 
| 8 | (GMT +8:00) Beijing, Perth, Singapore, Hong Kong | 
| 9 | (GMT +9:00) Tokyo, Seoul, Osaka, Sapporo, Yakutsk | 
| 9.5 | (GMT +9:30) Adelaide, Darwin | 
| 10 | (GMT +10:00) Eastern Australia, Guam Vladivostok | 
| 11 | (GMT +11:00) Magadan, Solomon Islands, New Caledonia | 
| 12 | (GMT +12:00) Auckland, Wellington, Fiji, Kamchatka | 
Sample Code
PHP
<?php
    require_once('/usr/local/virtualizor/sdk/enduser.php');
    $key =  '';
    $pass = '';
    $ip = '';
    $admin = new Virtualizor_Enduser_API($ip, $key, $pass);
    $post = array();
    $post['editsettings'] = 1;
    $post['language'] = 'english';
    $post['skins'] = 'default';
    $post['timezone'] = '(GMT -3:30) Newfoundland';
    $output = $admin->usersettings($post);
    print_r(json_encode($output));
?>
Curl
curl -k -X POST -d "editsettings=1&language=polish&skins=default& 
timezone=1" -L 
"https://hostname:4083/index.php?act=usersettings&api=json& 
apikey=your_api_key&apipass=your_api_pass&do=1"
Output
{
    "uid": "321",
    "act": "usersettings",
    "timezone": 1,
    "timenow": "September 23, 2016, 5:38 am",
    "vpsid": "3008",
    "username": "test@test.com",
    "user_type": "2",
    "preferences": {
        "fname": "test",
        "lname": "test",
        "theme": "default",
        "language": "english",
        "timezone": 1
    },
    "url": "index.php?",
    "rdns": {
        "pdnsid": null
    },
    "support_link": "http://softaculous.com",
    "disable_login_logo": 1,
    "title": "Users Settings",
    "done": {
        "msg": "Your settings were saved successfully"
    },
    "skins": {
        "default": "default"
    },
    "languages": {
        "polish": "polish",
        "english": "english",
        "german": "german",
        "chinese": "chinese",
        "portuguese": "portuguese",
        "dutch": "dutch",
        "french": "french"
    },
    "timezones": [-12, -11, -10, -9, -8, -7, -6, -5, -4, -3.5, -3, -2, -1, 0, 1, 2, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 8, 9, 9.5, 10, 11, 12],
    "timezone_names": ["(GMT -12:00) Eniwetok, Kwajalein", "(GMT -11:00) Midway Island, Samoa", "(GMT -10:00) Hawaii", "(GMT -9:00) Alaska", "(GMT -8:00) Pacific Time (US & Canada)", "(GMT -7:00) Mountain Time (US & Canada)", "(GMT -6:00) Central Time (US & Canada), Mexico City", "(GMT -5:00) Eastern Time (US & Canada), Bogota, Lima", "(GMT -4:00) Atlantic Time (Canada), Caracas, La Paz", "(GMT -3:30) Newfoundland", "(GMT -3:00) Brazil, Buenos Aires, Georgetown", "(GMT -2:00) Mid-Atlantic", "(GMT -1:00 hour) Azores, Cape Verde Islands", "(GMT) Western Europe Time, London, Lisbon, Casablanca", "(GMT +1:00 hour) Brussels, Copenhagen, Madrid, Paris", "(GMT +2:00) Kaliningrad, South Africa", "(GMT +3:00) Baghdad, Riyadh, Moscow, St. Petersburg", "(GMT +3:30) Tehran", "(GMT +4:00) Abu Dhabi, Muscat, Baku, Tbilisi", "(GMT +4:30) Kabul", "(GMT +5:00) Ekaterinburg, Islamabad, Karachi, Tashkent", "(GMT +5:30) Bombay, Calcutta, Madras, New Delhi", "(GMT +6:00) Almaty, Dhaka, Colombo", "(GMT +6:30) Yangon, Myanmar", "(GMT +7:00) Bangkok, Hanoi, Jakarta", "(GMT +8:00) Beijing, Perth, Singapore, Hong Kong", "(GMT +9:00) Tokyo, Seoul, Osaka, Sapporo, Yakutsk", "(GMT +9:30) Adelaide, Darwin", "(GMT +10:00) Eastern Australia, Guam, Vladivostok", "(GMT +11:00) Magadan, Solomon Islands, New Caledonia", "(GMT +12:00) Auckland, Wellington, Fiji, Kamchatka"],
    "time_taken": "0.107"
}