class DateTime

def utc

DateTime.civil(2005, 2, 21, 10, 11, 12, Rational(-6, 24)).utc # => Mon, 21 Feb 2005 16:11:12 +0000
DateTime.civil(2005, 2, 21, 10, 11, 12, Rational(-6, 24)) # => Mon, 21 Feb 2005 10:11:12 -0600

Adjusts DateTime to UTC by adding its offset value; offset is set to 0. 
def utc
  new_offset(0)
end