Yes. You'll need to 'Manage' the webinar in your channel and go to 'Edit booking' in order to change the start date and/or time.
If you have enabled the email service for your channel, an automatic rescheduled notification email with be sent to those subscribers that have pre-registered to attend this webinar.
Note: We do not recommend rescheduling Pro webinars within 30 minutes prior to their scheduled time. If you attempt to reschedule a Pro webinar during this time, you'll be prompted to reschedule it for least 30 minutes after your originally scheduled start time.