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])))

[SkrOYC]

Short anwer:
Change the Date + Time VC to:

[Date]+TIME([Slot])

And the column type of that VC to DateTime.

Start Datetime can be:

[DateID].[YourVC]

[SanyaCLAUS]

@SkrOYC Yes, I tried it, initially my "slots" fields are of type time(), and VS is "datetime"

I solved this problem and I sincerely don't understand why it doesn't work.
I created a virtual string IDENTICAL to startDateTime...
And when I create a new entry, the virtual string applies the value, but the one I need does not...
But I fixed this problem by adding a bot that, when adding a new line, changes the values ​​of the field I need to the virtual line field.

And after reloading: 

[SkrOYC]

If your Slots column is alread basetype Time, you don't need to wrap [Slot] with Time().

Also, I've found that the expression assistant says there is a problem sometime when there isn't. It gets fixed after save.

Finally, I made a mistake with the expression, do this instead:

[Date]+[Slot]+"000:00:00"

[SanyaCLAUS]

@SkrOYC I also thought that it should not, but it appears after a reboot

[SkrOYC]

Remove TIME()

[SanyaCLAUS]

Doesn't matter, anyway still an error, But this is not a problem, thank you very much for trying to help, but I solved this problem with "workarounds"

[Steve]

DATETIME([Date]) + ([Slot] - "00:00:00")

[SanyaCLAUS]

@Steve @SkrOYC It's better, but... just see 🙂

p.s. I pick 7/14/2022 9:30:00

But this is not a problem, thank you very much for trying to help, but I solved this problem in a different way, albeit confusing

[SkrOYC]

[Date] is already Date type
[Slot] is Time type
"000:00:00" a Duration

Date + Duration is already DateTime, right? 🤔

[Steve]

Maybe? Off the top of my head, I don't know, so I chose to suggest something I was sure of. 🙂