def millennium(date)
      m = ((date.year.abs.to_i / 1000) + 1).ordinalize + ' millennium'
      return [m, BCE_SUFFIX].join(' ') if (date.year <= -1)
      m
    end
def millennium(date)
      m = ((date.year.abs.to_i / 1000) + 1).ordinalize + ' millennium'
      return [m, BCE_SUFFIX].join(' ') if (date.year <= -1)
      m
    end
Formats a CarbonDate::Date with millennium precision
 Returns:
 A human-readable string representing the Date