# File lib/mail/parsers/rfc2822.rb, line 3458
    def _nt_month_name
      start_index = index
      if node_cache[:month_name].has_key?(index)
        cached = node_cache[:month_name][index]
        if cached
          cached = SyntaxNode.new(input, index...(index + 1)) if cached == true
          @index = cached.interval.end
        end
        return cached
      end

      i0 = index
      if has_terminal?("Jan", false, index)
        r1 = instantiate_node(SyntaxNode,input, index...(index + 3))
        @index += 3
      else
        terminal_parse_failure("Jan")
        r1 = nil
      end
      if r1
        r0 = r1
      else
        if has_terminal?("Feb", false, index)
          r2 = instantiate_node(SyntaxNode,input, index...(index + 3))
          @index += 3
        else
          terminal_parse_failure("Feb")
          r2 = nil
        end
        if r2
          r0 = r2
        else
          if has_terminal?("Mar", false, index)
            r3 = instantiate_node(SyntaxNode,input, index...(index + 3))
            @index += 3
          else
            terminal_parse_failure("Mar")
            r3 = nil
          end
          if r3
            r0 = r3
          else
            if has_terminal?("Apr", false, index)
              r4 = instantiate_node(SyntaxNode,input, index...(index + 3))
              @index += 3
            else
              terminal_parse_failure("Apr")
              r4 = nil
            end
            if r4
              r0 = r4
            else
              if has_terminal?("May", false, index)
                r5 = instantiate_node(SyntaxNode,input, index...(index + 3))
                @index += 3
              else
                terminal_parse_failure("May")
                r5 = nil
              end
              if r5
                r0 = r5
              else
                if has_terminal?("Jun", false, index)
                  r6 = instantiate_node(SyntaxNode,input, index...(index + 3))
                  @index += 3
                else
                  terminal_parse_failure("Jun")
                  r6 = nil
                end
                if r6
                  r0 = r6
                else
                  if has_terminal?("Jul", false, index)
                    r7 = instantiate_node(SyntaxNode,input, index...(index + 3))
                    @index += 3
                  else
                    terminal_parse_failure("Jul")
                    r7 = nil
                  end
                  if r7
                    r0 = r7
                  else
                    if has_terminal?("Aug", false, index)
                      r8 = instantiate_node(SyntaxNode,input, index...(index + 3))
                      @index += 3
                    else
                      terminal_parse_failure("Aug")
                      r8 = nil
                    end
                    if r8
                      r0 = r8
                    else
                      if has_terminal?("Sep", false, index)
                        r9 = instantiate_node(SyntaxNode,input, index...(index + 3))
                        @index += 3
                      else
                        terminal_parse_failure("Sep")
                        r9 = nil
                      end
                      if r9
                        r0 = r9
                      else
                        if has_terminal?("Oct", false, index)
                          r10 = instantiate_node(SyntaxNode,input, index...(index + 3))
                          @index += 3
                        else
                          terminal_parse_failure("Oct")
                          r10 = nil
                        end
                        if r10
                          r0 = r10
                        else
                          if has_terminal?("Nov", false, index)
                            r11 = instantiate_node(SyntaxNode,input, index...(index + 3))
                            @index += 3
                          else
                            terminal_parse_failure("Nov")
                            r11 = nil
                          end
                          if r11
                            r0 = r11
                          else
                            if has_terminal?("Dec", false, index)
                              r12 = instantiate_node(SyntaxNode,input, index...(index + 3))
                              @index += 3
                            else
                              terminal_parse_failure("Dec")
                              r12 = nil
                            end
                            if r12
                              r0 = r12
                            else
                              @index = i0
                              r0 = nil
                            end
                          end
                        end
                      end
                    end
                  end
                end
              end
            end
          end
        end
      end

      node_cache[:month_name][start_index] = r0

      r0
    end