How To Show Events Based On The Date A User Selects

I would like to build a form that can replace what I am current using. 

I need to build drop down that have variants. 

I would like to have a drop down for the 4 different days/dates of my event and then for the corresponding available time slots to popup for that given day. 

What would be the most efficient way to make that happen?

The easiest way to make that happen would to create a dropdown menu with your days/dates.  Then, create your time slots using using one of our widgets that allows for limiting quantity:

https://widgets.jotform.com/widget/quantity_gift_registry

https://widgets.jotform.com/widget/inventory

https://widgets.jotform.com/widget/appointment_slots

One may work better than another depending on your needs.

Once those are set up, you can use conditions to show the appropriate events when the day/date is selected in your dropdown:

https://www.jotform.com/help/316-How-to-Show-or-Hide-Fields-Base-on-User-s-Answer