Expand Start Date to End Date with Series of EOMONTHs

Question

I have a data table containing ids with a start date and end date associated with both.

RowNo   AcNo     StartDate     EndDate
  1     R125     01/10/2017            


        

Answer 1

Try it as a nested For ... Next loop using DateDiff to determine the number of months. Collecting the progressive values in an array will speed up execution before dumping them back to the worksheet.

Option Explicit

Sub eoms()
    Dim a As Long, m As Long, ms As Long, vals As Variant
    With Worksheets("Sheet2")
        .Range("F1:G1") = Array("AcNo", "EOMONTHs")
        For a = 2 To .Cells(.Rows.Count, "B").End(xlUp).Row
            ms = DateDiff("m", .Cells(a, "C").Value2, .Cells(a, "D").Value2)
            ReDim vals(1 To ms + 1, 1 To 2)
            For m = 1 To ms + 1
                vals(m, 1) = .Cells(a, "B").Value2
                vals(m, 2) = DateSerial(Year(.Cells(a, "C").Value2), _
                                        Month(.Cells(a, "C").Value2) + m, _
                                        0)
            Next m
            .Cells(.Rows.Count, "F").End(xlUp).Offset(1, 0).Resize(UBound(vals, 1), UBound(vals, 2)) = vals
        Next a
        .Range(.Cells(2, "G"), .Cells(.Rows.Count, "G").End(xlUp)).NumberFormat = "mmm yy"
    End With
End Sub

VBA's DateSerial can be used as a EOMONTH generator by setting the day to zero of the following month.

Note in the following image that the generated months are the EOMONTH of each month in the series with mmm yy cell number formatting.

Answer 2

Only because you seem to be soliciting multiple options, here is one without VBA:

• Expand your table to the right with a formula (using structured references here):

---

=IF(EOMONTH(Table1[@[StartDate]:[StartDate]],COLUMNS($A:A))<Table1[@[EndDate]:[EndDate]],EOMONTH(Table1[@[StartDate]:[StartDate]],COLUMNS($A:A)),"")

• Use Power Query or Data Get & Transform to unPivot all except the first two columns: (easily done in the GUI, but I paste the code below for interest)

---

let
    Source = Excel.CurrentWorkbook(){[Name="Table1"]}[Content],
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"RowNo", Int64.Type}, {"AcNo", type text}, {"StartDate", type datetime}, {"EndDate", type datetime}, {"Column1", type datetime}, {"Column2", type datetime}, {"Column3", type datetime}, {"Column4", type datetime}, {"Column5", type datetime}, {"Column6", type datetime}, {"Column7", type datetime}, {"Column8", type datetime}, {"Column9", type datetime}, {"Column10", type datetime}, {"Column11", type datetime}, {"Column12", type datetime}, {"Column13", type datetime}, {"Column14", type datetime}, {"Column15", type datetime}, {"Column16", type datetime}, {"Column17", type datetime}, {"Column18", type datetime}, {"Column19", type datetime}, {"Column20", type datetime}, {"Column21", type datetime}, {"Column22", type datetime}, {"Column23", type datetime}, {"Column24", type datetime}, {"Column25", type datetime}, {"Column26", type datetime}, {"Column27", type datetime}, {"Column28", type datetime}, {"Column29", type datetime}, {"Column30", type datetime}, {"Column31", type datetime}, {"Column32", type datetime}, {"Column33", type datetime}, {"Column34", type datetime}}),
    #"Unpivoted Other Columns" = Table.UnpivotOtherColumns(#"Changed Type", {"RowNo", "AcNo"}, "Attribute", "Value"),
    #"Removed Columns" = Table.RemoveColumns(#"Unpivoted Other Columns",{"Attribute"}),
    #"Renamed Columns" = Table.RenameColumns(#"Removed Columns",{{"Value", "EOM Date"}}),
    #"Changed Type1" = Table.TransformColumnTypes(#"Renamed Columns",{{"EOM Date", type date}})
in
    #"Changed Type1"

• Sort the results by AcNo and then by Date:

Note that, when done this way, the first date is actually a BOM date, but if you format them as in your results, mmm yy, it'll look the same. And things are easily changed if that is an issue.

If having the first month as a BOM date is not desired:

• Change the formula to:

---

=IF(EOMONTH(Table1[@[StartDate]:[StartDate]],COLUMNS($A:A)-1)<=Table1[@[EndDate]:[EndDate]],EOMONTH(Table1[@[StartDate]:[StartDate]],COLUMNS($A:A)-1),"")

---

• When executing the Data Get & Transform, delete the StartDate column in the Query GUI editor, as this will not affect the other columns at that time.