Time Blocks On Event?

Ok, trying to make this easier on me.  Is there a way to do time blocks within an event.  So for example I have an Easter Egg Hunt coming up from 9AM to 3 PM.  We are doing registrations in 20 minute time blocks within the event.  
I think when I did one before (fishing derby) I just ended up creating multiple events to cover different time blocks.  Is that the only way?

Thanks
 

There is other options to setup :

1. Use Ticket Types, so each ticket type is a time block. See eventbookingdoc.joomservices.com/plugins/ticket-types

2. Or create custom field (Select/List) custom field to allow choosing The Timeblock

Tuan