How to change Group User timezone?

When a Group User is created, there is no timezone field in both Create and Edit views.
I have several Group users and if a Calendar event is assigned to them, the group members
receive a message with the wrong timezone UTC (+00:00) instead of +5:00.
Does it happen because these Group Users were created with the wrong default timezone?
If so, how the timezone of the Group User can be changed?

You generally set the time zone in the individual user’s preferences.

I understand this. But if a Group User is created and an event is scheduled in this Group User’s shared Calendar, the Calendar itself shows correct time zone but all invitation letters has the wrong UTC (+00:00) time zone.

Any solution to this yet?
In our company we created a “All Employees” group user whose Calendar is being shared by everybody.
All company-wide events are scheduled in this calendar.
While the time of the events in this group user calendar is correct, the emails invitations sent to employees
contain a wrong time - UTC (+00:00) time zone.
This is serious enough bug to fix, I suppose.

Hi, all!
Does someone know where in code/database/CRM files I can find user settings of timezone? I need this to change by code or sql query (not from admin menu).

I’ve already solved this issue)
Maybe there is more simple way to solve this but here’s my solution (maybe it’ll help someone), see following:
In DB you can find only name of time zone. You can find it in [user_preferences] table in [contents] column encoded in base64. But there is no time offset of this timezone.
To get timezone offset from that column in DB we have to write it at the same time when we click on “Save” button (while creating or editing user).

To do this GOTO: \modules\Users, open file “Save.php” and after (nearly 378 line)
“$GLOBALS[‘sugar_config’][‘disable_team_access_check’] = true;
you have to insert following code:
// adding timeZone offset to [user_preferences][contents]
$userTimeZoneOffset = $focus->getUserDateTimePreferences();
$userTimeZoneOffset = $userTimeZoneOffset[‘userGmt’];

$indexOfGTM = strpos($userTimeZoneOffset,“GMT”);
$userTimeZoneOffset = substr($userTimeZoneOffset, $indexOfGTM + 3);
$userTimeZoneOffset = rtrim($userTimeZoneOffset, “)”);

$focus->setPreference(‘timezoneOffset’, $userTimeZoneOffset, 0, ‘global’);
// end of my code

P.S. you have to spend a bit time to make sql request for getting this value from encoded string.