From the Dashboard, go to Call Center and select Campaigns.
Under Show Campaigns, Click on the Action Button and select Settings.
Within the Campaign Settings, click on the Leads tab.
Scroll down to Outbound Filters Section
If you need to use a specific Timezone, choose from the option in GMT Lead Filter Override. Otherwise leave it as No Filter.
Select the calling hours for the campaign
If you need to add custom call times, you can create your own. Go to this link for more information.
Click on Apply Changes button to save the settings.