I think I would build the list by some fancy looping, but you can get close with SQL.

First create a table or a query that will return 10 numbers named TEN:

SELECT DISTINCT [Id] Mod 10 AS Factor
FROM MSysObjects
WHERE MSysObjects.Id > 0

and an INOUT table having one field INOUT and two records:

IN  
OUT

Next, create a UNION query, ALLABSEN:

SELECT 
    ID2, INOUT, DATEABSEN, [TIME], STATUS
FROM 
    ABSEN
UNION 
SELECT 
    ID2, INOUT, DATEABSEN, [TIME], STATUS
FROM 
    HELPERABSEN

and a Cartesian query, ALLDATES, to generate all dates:

SELECT 
    PERIOD.PERIODNAME, [Factor]+[STARTDATE] AS [DATE]
FROM 
    PERIOD, 
    TEN
WHERE 
    [Factor]+[STARTDATE] Between [STARTDATE] And [ENDDATE]
ORDER BY 
    [Factor]+[STARTDATE]

and yet a Cartesian query, ALLID2DATES, to return all possible entries:

SELECT 
    MASTERID2.ID2, MASTERID2.NAMEID2, INOUT.INOUT, ALLDATES.Date
FROM 
    MASTERID2, 
    ALLDATES, 
    INOUT
WHERE
    MASTERID2.POSITION = 'STAFF'
ORDER BY 
    ALLDATES.Date, MASTERID2.ID2, INOUT.INOUT;

Finally, you can assemble the output query, ID2ALLABSEN:

SELECT 
    ALLID2DATES.ID2, ALLID2DATES.NAMEID2, ALLID2DATES.INOUT, ALLID2DATES.DATE, ALLABSEN.TIME, ALLABSEN.STATUS
FROM 
    ALLID2DATES 
LEFT JOIN 
    ALLABSEN 
    ON (ALLID2DATES.DATE = ALLABSEN.DATEABSEN) AND (ALLID2DATES.INOUT = ALLABSEN.INOUT) AND (ALLID2DATES.ID2 = ALLABSEN.ID2)
ORDER BY 
    ALLID2DATES.DATE, ALLID2DATES.ID2, ALLID2DATES.INOUT, [DATE]+[ALLABSEN].[TIME]

Output:

Did you try altering values of GetStockSearching function in the ABSENservice class that includes a startDate and endDate paramater?

something like this :

Public Function GetStockSearching(startDate As Date, endDate As Date) As IEnumerable(Of ABSEN)
    Dim sql = $"SELECT ABSEN.ID2 AS [ID2], MASTERID2.NAMEID2 AS [NAMEID2], ABSEN.INOUT AS [INOUT], ABSEN.DATEABSEN AS [DATEABSEN], Format(ABSEN.TIME,'hh:mm:ss') AS [TIME], ABSEN.STATUS AS [STATUS] " &
              $"FROM ABSEN INNER JOIN MASTERID2 ON ABSEN.ID2 = MASTERID2.ID2 " &
              $"WHERE ABSEN.DATEABSEN BETWEEN #{startDate:yyyy-MM-dd}# AND #{endDate:yyyy-MM-dd}#"

    Using _conn = New OleDbConnection(GetOledbConnectionString())
        Return _conn.Query(Of ABSEN)(sql).ToList()
    End Using
End Function

Try adding two params startDate and endDate, which are both of type Date, they will be used to filter the ABSEN tables DATEABSEN column using the BETWEEN operator in SQL query.

To use this updated func, call it from Form1_Load event handler and pass in the desired start and end date as arguments.