Calculate Start and End Time that are Text

In this example I show the intermediate steps to show, but you don't need to include these...

declare @YourTable table (StartTimeText varchar(10), EndTimeText varchar(10))
insert into @YourTable select '70500', '71002'

select 
    *,
    cast(
       substring(right('000000'+StartTimeText,6),1,2)
       + ':' +
       substring(right('000000'+StartTimeText,6),3,2)
       + ':' +
       substring(right('000000'+StartTimeText,6),5,2) 
    as datetime),
    cast(
       substring(right('000000'+EndTimeText,6),1,2)
       + ':' +
       substring(right('000000'+EndTimeText,6),3,2)
       + ':' +
       substring(right('000000'+EndTimeText,6),5,2) 
    as datetime),
    cast(
    cast(
       substring(right('000000'+EndTimeText,6),1,2)
       + ':' +
       substring(right('000000'+EndTimeText,6),3,2)
       + ':' +
       substring(right('000000'+EndTimeText,6),5,2) 
    as datetime) - 
    cast(
       substring(right('000000'+StartTimeText,6),1,2)
       + ':' +
       substring(right('000000'+StartTimeText,6),3,2)
       + ':' +
       substring(right('000000'+StartTimeText,6),5,2) 
    as datetime)
    as time) as ElapsedTime
from @YourTable

gives

StartTimeText EndTimeText                                                 ElapsedTime
------------- ----------- ----------------------- ----------------------- ----------------
70500         71002       1900-01-01 07:05:00.000 1900-01-01 07:10:02.000 00:05:02.0000000

This should run on any version. --First the integer version

    DECLARE @YourTable TABLE (StartTime int,  EndTime int)

    INSERT  INTO @YourTable SELECT  70500, 71002
    INSERT  INTO @YourTable SELECT  120501, 121845


    SELECT  StartTime, EndTime,
            CONVERT(CHAR(8), (DATEADD(SECOND, DATEDIFF(SECOND,
                 CONVERT(DATETIME,CONVERT(VarCHAR(02),Starttime/10000)+':'
                 +CONVERT(VARCHAR(02),(StartTiME/100)%100)+':'
                 +CONVERT(VARCHAR(02),StartTime%100),8),
                  CONVERT(DATETIME,CONVERT(VarCHAR(02),Endtime/10000)+':'
                 +CONVERT(VARCHAR(02),(EndTime/100)%100)+':'
                  +CONVERT(VARCHAR(02),EndTime%100),8)),
               CONVERT(DATETIME, '00:00:00', 113))),8)                   
             AS ElapsedTime
    FROM    @YourTable 

--And now the string version

    DECLARE @YourTable TABLE (StartTimeText VARCHAR(10),
                              EndTimeText VARCHAR(10))

    INSERT  INTO @YourTable SELECT  '70500', '71002'
    INSERT  INTO @YourTable SELECT  '120501', '121845'

    SELECT  StartTimeText, EndTimeText,
            CONVERT(CHAR(8), (DATEADD(SECOND,
               DATEDIFF(SECOND,
                  CONVERT(DATETIME, STUFF(STUFF(LEFT('00',
                          6 - LEN(StartTimeText)) + StartTimeText,
                          5, 0, ':'), 3, 0,
                          ':'), 8),
                  CONVERT(DATETIME,  STUFF(STUFF(LEFT('00',
                          6 - LEN(EndTimeText)) + EndTimeText,
                          5, 0, ':'), 3, 0,
                          ':'), 8)),
               CONVERT(DATETIME, '00:00:00', 113))), 8)
             AS ElapsedTime
    FROM    @YourTable 

The measurement is a daily query. The activity is measured with the getdate() of that dady only so it all will be under 24 hours.

The users are pulling orders within a time period. if anything could check if > 1800 since they would never go past that time daily.

I just noticed the time is not string but it is being stored as int.

So now I get this error when I change the variables to int

Msg 242, Level 16, State 3, Line 10 The conversion of a varchar data type to a datetime data type resulted in an out-of-range value.

That error matches the query I am using for the real data too