Adjust scale of the horizontal axis in a Chart with VBA - excel

Question

I am trying to create a chart with VBA, collecting data with the code from a table (not selecting directly the data in the worksheet but doing some internal calculation). My problem is that it does not draw correctly the X-axis (it should be showing just 12.19, 01.20, 02.20):
Do you know how to adjust this (as each month has a different amount of days...)?
This is my code:
Function ChartGenerator(mes As Double, contrato As String, kpi As String)
Dim listax() As Double
Dim listay() As Double
Dim numeelem As Integer
numeelem = 0
last_row = Worksheets("Data").Range("A" & Rows.Count).End(xlUp).row
For i = 2 To last_row
If Worksheets("Data").Cells(i, 8).value <= mes And Worksheets("Data").Cells(i, 4).value = contrato _
And Worksheets("Data").Cells(i, 5).value = kpi Then
numeelem = numeelem + 1
End If
Next i
ReDim listax(numeelem - 1)
ReDim listay(numeelem - 1, 1)
numeelem = 0
For i = 2 To last_row
If Worksheets("Data").Cells(i, 8) <= mes And Worksheets("Data").Cells(i, 4) = contrato _
And Worksheets("Data").Cells(i, 5) = kpi Then
numeelem = numeelem + 1
listax(numeelem - 1) = Worksheets("Data").Cells(i, 8).value **'Those are dates**
listay(numeelem - 1, 0) = Worksheets("Data").Cells(i, 6).value
listay(numeelem - 1, 1) = Worksheets("Data").Cells(i, 7).value
End If
Next i
Dim ydata As Variant
ReDim ydata(numeelem - 1)
Charts.Add
With ActiveChart
.ChartArea.ClearContents
.ChartType = xlXYScatterLines
.ChartStyle = 241 'para cambiar el estilo, usar este
For k = 1 To 2
For j = 0 To numeelem - 1
ydata(j) = listay(j, k - 1)
Next j
.SeriesCollection.NewSeries
.SeriesCollection(k).XValues = listax
.SeriesCollection(k).Values = ydata
.SeriesCollection(k).Name = Worksheets("Data").Cells(1, 6 - 1 + k).value '"prueba" & i 'ID(i, 1)
If k = 2 Then
.SeriesCollection(k).Format.Line.DashStyle = msoLineSysDash
End If
For j = 1 To numeelem
With .SeriesCollection(k).Points(j)
.ApplyDataLabels
.DataLabel.Text = listay(j - 1, k - 1)
End With
Next j
Next k
.HasTitle = True
.Legend.Format.TextFrame2.TextRange.Font.Size = 14
.ChartTitle.Text = contrato & " - " & kpi
With .Axes(xlCategory, xlPrimary)
.HasTitle = True
.AxisTitle.Characters.Text = "Date"
.AxisTitle.Font.Size = 14
.AxisTitle.Font.Name = "calibri"
.CategoryType = xlTimeScale
.MinimumScale = listax(0) - 0.0000000001
.MaximumScale = listax(numeelem - 1) + 1
.MinorUnit = 31
.MajorUnit = 31
.TickLabels.NumberFormat = "mmmm-yy"
End With
With .Axes(xlValue, xlPrimary)
.HasTitle = True
.AxisTitle.Text = "Amount of €"
.AxisTitle.Font.Size = 14
.AxisTitle.Font.Name = "calibri"
End With
End With
End Function