Task: Cheryl's birthday
Python: 

from itertools import groupby
from re import split



def main():
    

    month, day = 0, 1
    print(
        
        
        uniquePairing(month)(
            
            
            uniquePairing(day)(
                
                
                monthsWithUniqueDays(False)([
                    
                    tuple(x.split()) for x in
                    split(
                        ', ',
                        'May 15, May 16, May 19, ' +
                        'June 17, June 18, ' +
                        'July 14, July 16, ' +
                        'Aug 14, Aug 15, Aug 17'
                    )
                ])
            )
        )
    )





def monthsWithUniqueDays(blnInclude):
    
    def go(xs):
        month, day = 0, 1
        months = [fst(x) for x in uniquePairing(day)(xs)]
        return [
            md for md in xs
            if blnInclude or not (md[month] in months)
        ]
    return go



def uniquePairing(i):
    
    def go(xs):
        def inner(md):
            dct = md[i]
            uniques = [
                k for k in dct.keys()
                if 1 == len(dct[k])
            ]
            return [tpl for tpl in xs if tpl[i] in uniques]
        return inner
    return ap(bindPairs)(go)





def bindPairs(xs):
    
    return lambda f: f(
        (
            dictFromPairs(xs),
            dictFromPairs(
                [(b, a) for (a, b) in xs]
            )
        )
    )



def dictFromPairs(xs):
    
    return {
        k: [snd(x) for x in m] for k, m in groupby(
            sorted(xs, key=fst), key=fst
        )
    }





def ap(f):
    
    def go(g):
        def fxgx(x):
            return f(x)(
                g(x)
            )
        return fxgx
    return go



def fst(tpl):
    
    return tpl[0]



def snd(tpl):
    
    return tpl[1]


if __name__ == '__main__':
    main()

VB: Private Sub exclude_unique_days(w As Collection)
    Dim number_of_dates(31) As Integer
    Dim months_to_exclude As New Collection
    For Each v In w
        number_of_dates(v(1)) = number_of_dates(v(1)) + 1
    Next v
    For i = w.Count To 1 Step -1
        If number_of_dates(w(i)(1)) = 1 Then
            months_to_exclude.Add w(i)(0)
            w.Remove i
        End If
    Next i
    For Each m In months_to_exclude
        exclude_month w, m
    Next m
End Sub
Private Sub exclude_month(x As Collection, v As Variant)
    For i = x.Count To 1 Step -1
        If x(i)(0) = v Then x.Remove i
    Next i
End Sub
Private Sub exclude_non_unique_days(w As Collection)
    Dim number_of_dates(31) As Integer
    For Each v In w
        number_of_dates(v(1)) = number_of_dates(v(1)) + 1
    Next v
    For i = w.Count To 1 Step -1
        If number_of_dates(w(i)(1)) > 1 Then
            w.Remove i
        End If
    Next i
End Sub
Private Sub exclude_non_unique_months(w As Collection)
    Dim months As New Collection
    For Each v In w
        On Error GoTo 1
        months.Add v(0), v(0)
    Next v
1:
    For i = w.Count To 1 Step -1
        If w(i)(0) = v(0) Then
            w.Remove i
        End If
    Next i
End Sub
Public Sub cherylsbirthday()
    Dim v As New Collection
    s = "May 15, May 16, May 19, June 17, June 18, July 14, July 16, August 14, August 15, August 17"
    t = Split(s, ",")
    For Each u In t
        v.Add Split(Trim(u), " ")
    Next u
    
    exclude_unique_days v
    
    exclude_non_unique_days v
    
    exclude_non_unique_months v
    Debug.Print v(1)(0); " "; v(1)(1)
End Sub