# File lib/time.rb, line 261
    def rfc2822(date)
      if /\A\s*
          (?:(?:Mon|Tue|Wed|Thu|Fri|Sat|Sun)\s*,\s*)?
          (\d{1,2})\s+
          (Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)\s+
          (\d{2,})\s+
          (\d{2})\s*
          :\s*(\d{2})\s*
          (?::\s*(\d{2}))?\s+
          ([+-]\d{4}|
           UT|GMT|EST|EDT|CST|CDT|MST|MDT|PST|PDT|[A-IK-Z])/ix =~ date
        # Since RFC 2822 permit comments, the regexp has no right anchor.
        day = $1.to_i
        mon = MonthValue[$2.upcase]
        year = $3.to_i
        hour = $4.to_i
        min = $5.to_i
        sec = $6 ? $6.to_i : 0
        zone = $7

        # following year completion is compliant with RFC 2822.
        year = if year < 50
                 2000 + year
               elsif year < 1000
                 1900 + year
               else
                 year
               end

        year, mon, day, hour, min, sec =
          apply_offset(year, mon, day, hour, min, sec, zone_offset(zone))
        t = self.utc(year, mon, day, hour, min, sec)
        t.localtime if !zone_utc?(zone)
        t
      else
        raise ArgumentError.new("not RFC 2822 compliant date: #{date.inspect}")
      end
    end