class ActiveSupport::TimeWithZone

def dst?

Time.zone.parse("2012-11-30").dst? # => false
Time.zone.parse("2012-5-30").dst? # => true
Time.zone = 'Eastern Time (US & Canada)' # => 'Eastern Time (US & Canada)'

specified time zone.
Returns true if the current time is within Daylight Savings Time for the 
def dst?
  period.dst?
end