ruby time confusion

gistfile1.txt

$ export TZ=MST
$ bundle exec rails c
ruby-1.9.3-p0 :001 >  t = Time.new(2013, 1, 1, 0, 0, 0, "+00:00")
 => 2013-01-01 00:00:00 +0000 
ruby-1.9.3-p0 :002 > t + 1.day
 => 2013-01-02 00:00:00 -0700 
ruby-1.9.3-p0 :003 > t + 1.day.to_i
 => 2013-01-02 00:00:00 +0000 
ruby-1.9.3-p0 :004 > 1.day.object_id
 => 172801 
ruby-1.9.3-p0 :005 > 1.day.to_i.object_id
 => 172801