Pattern matching against Dates in Elixir

Dates in Elixir aren't native values, so there aren't any guard clause functions available for use with date/datetime. You can, however, use pattern matching:

def foo(%Date{} = date) do
  Timex.to_naive_datetime(date) |> foo
end

def foo(%DateTime{} = datetime) do
  Timex.to_naive_datetime(datetime) |> foo
end

def foo(%NaiveDateTime{} = datetime) do
  IO.inspect({"My Naive Datetime", datetime})
end