Limiting access to social networking sites to a number of minutes per day is an effective control mechanism that minimizes waste of time, while at the same time enables social network sites for a small amount of time per day.
To do this, click Manage, select the Policies option, click Add Policy, give the new policy a name and add a description. Set the new policy to Block and then drag and drop the Websites Element. Select the Social Network Category from the list provided and click Add to Policy. Drag and drop the Time Element, set the duration that allows access to Social Networking sites, in this case we're limiting access to 30 minutes per day. Check that the required policy conditions are ok and Save the new policy.