code: def get_date(layer):
      
      date = None
      sign = '+'
      date_type = 1
      layer_dates = layer.get_layer_dates()
      # we index the first date!
      if layer_dates:
          sign = layer_dates[0][0]
          date = layer_dates[0][1]
          date_type = layer_dates[0][2]
      if date is None:
          date = layer.created
      # layer date > 2300 is invalid for sure
      # TODO put this logic in date miner
      if date.year > 2300:
          date = None
      if date_type == 0:
          date_type = "Detected"
      if date_type == 1:
          date_type = "From Metadata"
      return get_solr_date(date, (sign == '-')), date_type
docs: Returns a custom date representation. A date can be detected or from metadata.
      It can be a range or a simple date in isoformat.