Disney has made some huge changes to the DAS system at Disney World including doubling the validity period from 120 to 240 days. This comes not too long after changing the rules of who is eligible and how you register for this service.
Registration at Walt Disney World now occurs solely via video chat, no longer available at in-park Guest Relations locations. This can be completed up to 30 days before your visit.
This is a big change since before you could register via video chat, but you also had the opportunity to register in the parks by talking to a Cast Member in person.
If you don’t enroll in DAS before your park visit, you will now be directed to a location where you will still have a virtual chat on an iPad to determine eligibility.
So it is possible to do a same-day reservation, but you will be wasting precious park time to do it, which we obviously don’t recommend.