RegEx MM DD YYYY to YYYY MM DD

问题

I am new here and almost as new to RegEx. I am trying to use a RegEx expression to convert dates in a string in this format 05-18-16 or 5-18-16 or 05 18 16 or 5 18 16 to YYYY MM DD format.

Note the dates in the string can be YY or YYYY.

I have the "Find" expression working, but having trouble with the replacement. I found some code on this site that I thought would work, but the result is always "1900 1 31" and not 2016 05 18"

Sub StackExPost()
Dim strIn As String, strReturn As String
  strIn = "Test 05 09 16 and 5-9-2016 Test"
  strReturn = fcnRegEx(strIn, "\b(0?[1-9]|1[0-12])( |-)(0?[1-9]|[1-2][0-9]|3[0-1])( |-)((?:\d{4}|\d{2}))", "$5 $3 $1")
  MsgBox strReturn 'I get get and transpose the components.
  strReturn = fcnRegEx(strIn, "\b(0?[1-9]|1[0-12])( |-)(0?[1-9]|[1-2][0-9]|3[0-1])( |-)((?:\d{4}|\d{2}))", Format("$5", "YYYY") & " " & Format("$2", "MM") & " " & Format("$1", "DD"))
  MsgBox strReturn '... but can't apply the formatting.
End Sub
Function fcnRegEx(strIn As String, strPattern As String, Optional strReplace As String = vbNullString, Optional bGlobal As Boolean = True)
Dim objRegex As Object
Dim objRegM As Object
  Set objRegex = CreateObject("vbscript.regexp")
  objRegex.Global = bGlobal
  With objRegex
    .IgnoreCase = True
    .Pattern = strPattern
    If .Test(strIn) Then
      Set objRegM = .Execute(strIn)
      If strReplace = vbNullString Then
        fcnRegEx = objRegM(0).Value 'submatches(0)
      Else
        fcnRegEx = objRegex.Replace(strIn, strReplace)
      End If
    Else
      fcnRegEx = "//No Match\\"
    End If
  End With
lbl_Exit:
  Exit Function
End Function

Thank you all for reading and for any guidance provided.

回答1:

Start by adding leading zeros first by using this pattern first

\b(?=\d\b)

and replace with 0
Demo

then apply this pattern on the results

^(\d+)\D*(\d+)\D*(\d\d)$

and replace with 20$3 $1 $2
Demo

来源：https://stackoverflow.com/questions/37305359/regex-mm-dd-yyyy-to-yyyy-mm-dd

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regex

date