class DateTime

def utc

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

Returns a Time instance of the simultaneous time in the UTC timezone. 
def utc
  utc = new_offset(0)
  Time.utc(
    utc.year, utc.month, utc.day,
    utc.hour, utc.min, utc.sec + utc.sec_fraction
  )
end