docs: def __check_time_values(self):
          """
          Rules
          1. AD or CE units: bigger number is recent, smaller number is older
          2. BP: bigger number is older, smaller number is recent.
          3. No units: If max year is 1900-2017(current), then assume AD. Else, assume BP
  
          :return none:
          """
          _earliest = float(self.noaa_data_sorted["Data_Collection"]["Earliest_Year"])
          _recent = float(self.noaa_data_sorted["Data_Collection"]["Most_Recent_Year"])
          try:
              _unit = self.noaa_data_sorted["Data_Collection"]["Time_Unit"]
          except Exception:
              _unit = ""
  
          if not _unit:
              # If the max value is between 1900 - 2017 (current), then assume "AD"
              _max = max([_earliest, _recent])
              _min = min([_earliest, _recent])
              if _max >= 1900 and _max <= 2018:
                  self.noaa_data_sorted["Data_Collection"]["Time_Unit"] = "AD"
                  self.noaa_data_sorted["Data_Collection"]["Most_Recent_Year"] = str(_max)
                  self.noaa_data_sorted["Data_Collection"]["Earliest_Year"] = str(_min)
              # Else, assume it's BP
              else:
                  # Units don't exist, assume BP
                  self.noaa_data_sorted["Data_Collection"]["Time_Unit"] = "BP"
                  self.noaa_data_sorted["Data_Collection"]["Most_Recent_Year"] = str(_min)
                  self.noaa_data_sorted["Data_Collection"]["Earliest_Year"] = str(_max)
          else:
              # Units exist
              if _unit.lower() in ["ad", "ce"]:
                  if _earliest > _recent:
                      self.noaa_data_sorted["Data_Collection"]["Most_Recent_Year"] = str(_earliest)
                      self.noaa_data_sorted["Data_Collection"]["Earliest_Year"] = str(_recent)
              else:
                  if _recent > _earliest:
                      self.noaa_data_sorted["Data_Collection"]["Most_Recent_Year"] = str(_earliest)
                      self.noaa_data_sorted["Data_Collection"]["Earliest_Year"] = str(_recent)
  
          return