class_docstr: Date abscissa xy graph class
docstr: Return the value formatter for this graph
docstr_tok: ["Return","the","value","formatter","for","this","graph"]
code: def _x_format(self):
      """Return the value formatter for this graph"""
  
      def date_to_str(x):
          d = datetime.utcfromtimestamp(x).date()
          return self.x_value_formatter(d)
  
      return date_to_str
  
imports: from datetime import date, datetime, time, timedelta
  from pygal._compat import timestamp
  from pygal.adapters import positive
  from pygal.graph.xy import XY
label_desc: Use image node_id 1 for calling the DateLine obj's underlying member method code with example usage: obj._x_format() and returns: date_to_str, self