:except not working as expected

[wbasmayor]

Scenario

r = Recurrence.new( {:interval=>3, :starts=>Wed, 31 Aug 2016, :until=>Mon, 31 Oct 2016, :except=>[Sat, 03 Sep 2016, Sun, 04 Sep 2016, Sat, 10 Sep 2016, Sun, 11 Sep 2016, Sat, 17 Sep 2016, Sun, 18 Sep 2016, Sat, 24 Sep 2016, Sun, 25 Sep 2016, Sat, 01 Oct 2016, Sun, 02 Oct 2016, Sat, 08 Oct 2016, Sun, 09 Oct 2016, Sat, 15 Oct 2016, Sun, 16 Oct 2016, Sat, 22 Oct 2016, Sun, 23 Oct 2016, Sat, 29 Oct 2016, Sun, 30 Oct 2016]})

Note: The :except dates are basically excluding all saturday and sunday.

Expected Dates:
Aug 31, Sept 5, Sept 8, Sept 13

Results:
Aug 31, Sept 6, Sept 9, Sept 12

If you can see, it got messed up during Sept 5 instead appearing on Sept 6.

Aug 31 is wednesday so on the 3rd day excluding sat sun should have been Sept 5.