Rails date subtraction different on Mac OS and Linux

gistfile1.rb

# Using ruby-2.0.0-p247, Rails console

# On Mac:
2.0.0p247 :006 > Date.today - Date.yesterday
 => 1 
2.0.0p247 :007 > (Date.today - Date.yesterday).class
 => Fixnum 

# On Ubuntu 12.04
2.0.0p247 :009 > Date.today - Date.yesterday
 => (1/1) 
2.0.0p247 :010 > (Date.today - Date.yesterday).class
 => Rational 

# When I try to unload ActiveSupport extensions, I still see different behavior for Date:
# Mac OS X:
2.0.0-p247 :001 > Date.ancestors
 => [Date, Comparable, Object, Kernel, BasicObject] 

# Linux
2.0.0p247 :002 > Date.ancestors
 => [Date, Object, Kernel, BasicObject] 

# Something is still monkey-patching my Date? The initializers are also different - on OS X it takes three params (Y, M, D) and on Linux I get:
2.0.0p247 :006 > ::Date.new(2011, 01, 03)
ArgumentError: wrong number of arguments (3 for 0)

# OS X:
2.0.0-p247 :005 > Date.new(2001, 1, 1)
 => #<Date: 2001-01-01 ((2451911j,0s,0n),+0s,2299161j)>