module DateAndTime::Calculations

def beginning_of_year

now.beginning_of_year # => Thu, 01 Jan 2015 00:00:00 +0000
now = DateTime.current # => Fri, 10 Jul 2015 18:41:29 +0000

+DateTime+ objects will have a time set to 0:00.

today.beginning_of_year # => Thu, 01 Jan 2015
today = Date.today # => Fri, 10 Jul 2015

Returns a new date/time at the beginning of the year. 
def beginning_of_year
  change(month: 1).beginning_of_month
end