VBA how to use date to write file name in PDF

[wdg1]

How do I use "date document" for a PDF file name?
The declaration of "document date" causes an error:

Dim datedoc As Date
Then I use datedoc to my PDF-file name which does not work.

Sub InvoiceToPdf()
Dim volgnr As Long
Dim slo As String
Dim Toganr As Long
Dim bedrag As Currency
Dim fname As String
Dim datedoc As Date
volgnr = Range("B1")
slo = Range("B2")
Toganr = Range("B3")
bedrag = Range("B4")
Path = "C:\Users\gebruiker\factuur"
' this works not, the datedoc causes error
fname = Toganr & " - " & slo & " - " & volgnr & " - " & datedoc
ActiveSheet.ExportAsFixedFormat Type:=xlTypePDF, ignoreprintareas:=False, Filename:=Path & fname
End Sub

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Thanks, Ward