SQL - Spilt timestamp into multiple rows

I am dealing with data that needs to be looked at on a shift-to-shift basis (8:00:00 to 20:00:00 and its reciprocal are the two shifts) There are instances where a timestamp (one row) will span longer than a shift. Below is an example of what I am looking for.

----------------------------------------------------------------------------------------------------------
                                           Original Timestamp Data
----------------------------------------------------------------------------------------------------------
   START_TIME             END_TIME
2020-07-16 04:54:50	 2020-07-27 06:36:14

----------------------------------------------------------------------------------------------------------
                                           Updated Timestamp Data
---------------------------------------------------------------------------------------------------------
-
   START_TIME             END_TIME
2020-07-16 04:54:50	 2020-07-16 08:00:00
2020-07-16 08:00:00	 2020-07-16 20:00:00
2020-07-16 20:00:00	 2020-07-17 08:00:00
2020-07-17 08:00:00	 2020-07-17 20:00:00
        .                      .
        .                      .
        .                      .
2020-07-26 20:00:00  2020-07-27 06:36:14

Here is the code I have tried but I am only able to split the data into two rows. SOmething tells me that the "Start Roll" and "End Roll" Columns within #T1 are not going to work in a situation like this.

Declare @DayTurn as DATETIME, @NightTurn As DATETIME, @TodaysDate As DATETIME, @DateCheck As DATETIME, @TimeChange As Integer, @MidNight As DATETIME

Set @DayTurn = '8:00:00'
Set @NightTurn = '20:00:00'
SET @TodaysDate = GETDATE()
SET @DateCheck = CASE WHEN DATEPART( WK, @TodaysDate) >= 7 THEN DATEADD(yy, DATEDIFF(yy, 0, GETDATE()), 0)
    ELSE DATEADD(Week,-6,DATEADD(yy, DATEDIFF(yy, 0, GETDATE()), 0))
END;

SELECT  	
      (Case 
	    When cast(Activity.[START_TIME_UTC] as time) >= cast(@DayTurn as time) and cast(Activity.[END_TIME_UTC] as time) > cast(@NightTurn as time) and cast(Activity.[START_TIME_UTC]) as time)  cast(@DayTurn as time) then CONVERT(DATETIME, CONVERT(CHAR(8), Activity.[START_TIME_UTC] , 112) + ' ' + CONVERT(CHAR(8), @DayTurn, 108))
		else CONVERT(datetime, Activity.[START_TIME_UTC]) end) as 'Start Roll'
      ,(case
		When cast(Activity.[START_TIME_UTC] as time)  cast(@DayTurn as time) then CONVERT(DATETIME, CONVERT(CHAR(8), Activity.[START_TIME_UTC], 112) + ' ' + CONVERT(CHAR(8), @DayTurn, 108))
		else CONVERT(datetime, Activity.[END_TIME_UTC]) end ) As 'END_TIME'
	  ,(Case
		When cast(Activity.[START_TIME_UTC] as time) >= cast(@DayTurn as time) and cast(Activity.[END_TIME_UTC] as time) > cast(@NightTurn as time) and cast(Activity.[START_TIME_UTC] as time) = @DateCheck


SELECT * INTO #T2 from(
Select 
	temp.[START_TIME]
	,temp.[END_TIME]
From #T1 as temp
UNION
Select
	temp.[Start Roll]
	,temp.[End Roll]
From #T1 as temp
) as temp;


SELECT 
  *
FROM #T2 
Order By START_TIME;

Drop Table #T1
Drop Table #T2

Any and all help is greatly appreciated. Cheers!