def shift_dates(seconds)
      self.birthDatetime = (birthDatetime.utc.to_time + seconds.seconds).to_datetime
      dataElements.each { |element| element.shift_dates(seconds) }
    end
def shift_dates(seconds)
      self.birthDatetime = (birthDatetime.utc.to_time + seconds.seconds).to_datetime
      dataElements.each { |element| element.shift_dates(seconds) }
    end
Shift all data element fields that deal with dates by the given value.
 Given value should be in seconds. Positive values shift forward, negative
 values shift backwards.

 Note: This will shift dates of the birthdate and
 dates on the data elements that exist on the patient.