The Events Calendar stores the Event Start date with the field name: _EventStartDate
To use the "_EventStartDate" field with the view's ordering section, you will have to add it from the "Hidden custom fields" section that is available at:
=> Toolset => Settings => Frontend Content => Hidden custom fields section and click on button "Select custom fields" to add the field _EventStartDate.
Once you add the _EventStartDate custom field to "Hidden custom fields" section then you should refresh your page/view and then navigate to Ordering section and select the field "_EventStartDate" from the dropdown and save your view/page and check on the frontend.