Function IsInArray(ByVal MyDate As Date, ByRef Holiday_Calendar As Range) As Boolean
Dim length As Integer
length = WorksheetFunction.Count(Holiday_Calendar)
Dim counter As Integer
'counter = 0

For counter = 0 To length
If Holiday_Calendar(counter) = MyDate Then
IsInArray = True
End If
Next counter

IsInArray = False
End Function

Option Explicit

Private Sub DateArrays()

        Dim rngToPass As Range
        Dim dtMyDate As Date
        Dim containsDt As Boolean

        Set rngToPass = Sheet1.Range("A1:A4")
        dtMyDate = "8/7/2015"

        containsDt = IsInArray(dtMyDate, Application.WorksheetFunction.Transpose(rngToPass))

End Sub

Function IsInArray(ByVal MyDate As Date, ByRef Holiday_Calendar As Variant) As Boolean
        Dim length As Integer
        length = WorksheetFunction.Count(Holiday_Calendar)
        Dim counter As Integer

        For counter = 1 To length
                If Holiday_Calendar(counter) = MyDate Then
                        IsInArray = True
                        Exit Function
                End If
        Next counter

        IsInArray = False
End Function