Failing test in Ruby gigasecond exercise

[patbl]

I can't figure out why one of the tests in this exercise is failing (the other tests pass). I even tested it with the example solution:

# gigasecond.rb
class Gigasecond

  attr_reader :born_at
  def initialize(date_of_birth)
    @born_at = date_of_birth.to_time
  end

  def date
    (born_at + 1_000_000_000).to_date
  end

end

# gigasecond_test.rb
def test_2
  gs = Gigasecond.new(Date.new(1977, 6, 13))
  assert_equal Date.new(2009, 2, 19), gs.date
end

# output
  1) Failure:
GigasecondTest#test_2 [gigasecond_test.rb:15]:
--- expected
+++ actual
@@ -1 +1 @@
-#<Date: 2009-02-19 ((2454882j,0s,0n),+0s,2299161j)>
+#<Date: 2009-02-18 ((2454881j,0s,0n),+0s,2299161j)>

[kytrinyx]

Moved to exercism/ruby#7