code: def centred_timegrid(cls, simulationstep):
          
          simulationstep = Period(simulationstep)
          return Timegrid(
              cls._STARTDATE+simulationstep/2,
              cls._ENDDATE+simulationstep/2,
              simulationstep)
docs: Return a |Timegrid| object defining the central time points
          of the year 2000 for the given simulation step.
  
          >>> from hydpy.core.timetools import TOY
          >>> TOY.centred_timegrid('1d')
          Timegrid('2000-01-01 12:00:00',
                   '2001-01-01 12:00:00',
                   '1d')