code: def from_ad_date(cls, date):
          
          functions.check_valid_ad_range(date)
          days = values.START_EN_DATE - date
  
          # Add the required number of days to the start nepali date
          start_date = NepDate(values.START_NP_YEAR, 1, 1)
          # No need to update as addition already calls update
          return start_date + (date - values.START_EN_DATE)
docs: Gets a NepDate object from gregorian calendar date