change(options)
Instance Public methods
Returns a new Date where one or more of the
elements have been changed according to the options parameter.
The options parameter is a hash with a combination of these
keys: :year, :month, :day.
Date.new(2007, 5, 12).change(day: 1) # => Date.new(2007, 5, 1)
Date.new(2007, 5, 12).change(year: 2005, month: 1) # => Date.new(2005, 1, 12)