code: def spline_interpolate_by_datetime(datetime_axis, y_axis, datetime_new_axis):
      
      numeric_datetime_axis = [
          totimestamp(a_datetime) for a_datetime in datetime_axis
      ]
  
      numeric_datetime_new_axis = [
          totimestamp(a_datetime) for a_datetime in datetime_new_axis
      ]
  
      return spline_interpolate(
          numeric_datetime_axis, y_axis, numeric_datetime_new_axis)
docs: A datetime-version that takes datetime object list as x_axis