Problem with ref data

[SanyaCLAUS]

I have a date picker with time "slots"  (enum).

SLOTS FORMULA:

LIST(
"08:00:00", "08:30:00", "09:00:00", "09:30:00" 
"10:00:00", "10:30:00", "11:00:00", "11:30:00", 
"12:00:00", "12:30:00", "13:00:00", "13:30:00",
"14:00:00", "14:30:00", "15:00:00")

 - 

Select(
Reserved[Slots], [Date] = [_THISROW].[Date]
) 
- 
Select(Reserved[One hour], [Date] = [_THISROW].[Date]) - Select(Reserved[Two hour], [Date] = [_THISROW].[Date]) - Select(Reserved[One&half], [Date] = [_THISROW].[Date]) - Select(Reserved[Two&half], [Date] = [_THISROW].[Date])

They work on the principle: the user selects a date and selects an hour, in enum.

Then I add a condition to this list so that dates + hours do not repeat.

This works by reference type, for making appointments. I also add the start time value to the other sheet.

The problem is that I get absolutely no result (I think because of the misuse of types).

What formula should I use in my case for Start Datetime?

Here are some formulas that might help to better experience:

1. Date + time as a virtual column like... label: and how it look:

CONCATENATE([Date], " ", [Slots])

My formula for Start Datetime: 

DAtetime(Concatenate(Date([DateID].[Date]), " ", Time([DateID].[Slots])))