The default timezone for Social Report is CST - US Central Timezone.
Each project, however, can have its own custom timezone. When you are creating a project, you can select the time zone that you prefer. You can also change the project time zone at any time by going to Settings > Project.
Under Project Settings, click Modify Project Settings:
Setting the project level timezone offers a default timezone selection to all project users.
Each user, however, may decide to see the project data in their own timezone. The user can then change their project level timezone by clicking on the date range selector and choosing from an available list of time zones.