try fix for failing test

Author: nrednav

lib/msgpack/decoder.ex

@@ -233,7 +233,9 @@ defmodule Msgpack.Decoder do
       base_datetime = NaiveDateTime.from_erl!(erlang_datetime)
 
       if nanoseconds > 0 do
-        NaiveDateTime.add(base_datetime, nanoseconds, :nanosecond)
+        # NaiveDateTime.add(base_datetime, nanoseconds, :nanosecond)
+        microseconds = div(nanoseconds, 1000)
+        %{base_datetime | microsecond: {microseconds, 6}}
       else
         base_datetime
       end
@@ -250,7 +252,9 @@ defmodule Msgpack.Decoder do
       base_datetime = NaiveDateTime.from_erl!(erlang_datetime)
 
       if nanoseconds > 0 do
-        NaiveDateTime.add(base_datetime, nanoseconds, :nanosecond)
+        # NaiveDateTime.add(base_datetime, nanoseconds, :nanosecond)
+        microseconds = div(nanoseconds, 1000)
+        %{base_datetime | microsecond: {microseconds, 6}}
       else
         base_datetime
       end