There are two options for sending your broadcast - "Now" or "Later". The default option is "Now".
To schedule your job for a later date or time, select "Later" from the "Send Broadcast" drop down box at the end of the broadcast wizard. Select the date and time you wish to send your broadcast and click "OK" to submit.
You can schedule a job up to 28 days in the future. You can also cancel your scheduled job any time until it has been submitted.