Registration Start Date, explained
Specifying a Registration Start Date is required in order to get scheduling at the webinar event enabled.
Registration Start Date, can be used to delay any clients from registering to the webinar event, until such time as you have it completely setup. Its not reuired to adjust or change at an New Webinar and will come setup by default to some recent date when created.
Stealthseminar will not share or market you links to the event, only you have the ability to make your event links public by sharing or marketing the event links. With that in mind,you can start your webinar up by post dating the Registration Start Date, to test the webinar event by registering.
Duplicating your webinar event is also a recommended practice, to setup Registration Start Date at a new test or duplicated event.
Once registrations occur at the event, Registration Start Date is no longer available to edit.
Shown below in Scheduling section, setting for date/time.

You can find Registration End Date just below the setting.
Registration End Date: is a useful tool if you want date/times no longer available to choose from at the event's registration. It is Not required to setup and left blank by default, events wiil run until subscriptions end.