Jun 17, 2014

Change all user's default timezone setting for their MySite in SharePoint Online

In order to change the default timezone setting for the MySite in SharePoint Online:

1. Connect to SharePoint Online with an administrative account.
2. Go to the administrator's MySite.
3. Select Site Configuration from the menu.
4. Select Regional Settings from the Site Configuration screen.
5.  Choose the desired default timezone.  Click OK.
6. Done! All other users will inherit this default timezone.

To confirm the change:
1. Connect to SharePoint Online with a regular user account.
2. From the user name dropdown menu, select "About me"
3. From the user profile screen, click on "Edit profile".
4. Click on the three dot menu and select "Language and region"
5. In the section "Region", change the radio button "Choose your settings" from "Always use the regional settings defined by the site administrators" to "Always use my personal settings"
6.  Confirm that the default timezone in is the one chosen by the site administrator.
7.  Cancel out from the screen to leave the default setting.

Source: http://community.office365.com/en-us/f/148/t/175534.aspx