anchor.diff:           case localtime_dst:check(LocalDateTime, TzRule) of
               is_in_dst ->
                  adjust_datetime(UtcDateTime, invert_shift(DstShift));
  -            Res when (Res == is_not_in_dst) or (Res == ambiguous_time) ->
  +            is_not_in_dst ->
                  UtcDateTime;
  +            ambiguous_time ->
  +               [UtcDateTime, adjust_datetime(UtcDateTime, invert_shift(DstShift))];
               time_not_exists ->
                  time_not_exists
            end
      end.
   
  -% local_to_local(LocalDateTime, TimezoneFrom, TimezoneTo) -> LocalDateTime | tim_not_exists | {error, ErrDescr}
  +% local_to_local(LocalDateTime, TimezoneFrom, TimezoneTo) -> LocalDateTime | ambiguous | time_not_exists | {error, ErrDescr}
   %  LocalDateTime = DateTime()
   %  TimezoneFrom = String()
   %  TimezoneTo = String()
  
positive.code:             is_not_in_dst ->
                 LocalDateTime;
              ambiguous_time ->
                 RecheckIt = adjust_datetime(LocalDateTime, DstShift),
                 case localtime_dst:check(RecheckIt, TzRule) of
                    ambiguous_time ->
                       RecheckIt;
                    _ ->
                       LocalDateTime
                 end
           end
     end.
  
  % local_to_utc(LocalDateTime, Timezone) -> UtcDateTime | tim_not_exists | {error, ErrDescr}
  %  LocalDateTime = DateTime()
  %  Timezone = String()
  %  UtcDateTime = DateTime()
  %  ErrDescr = atom(), unknown_tz
  local_to_utc(LocalDateTime, Timezone) ->
     case lists:keyfind(get_timezone(Timezone), 1, ?tz_database) of
  
negative.code:      ,tz_shift/3
    ]).
  
  % utc_to_local(UtcDateTime, Timezone) -> LocalDateTime | [LocalDateTime, DstLocalDateTime] | {error, ErrDescr}
  %  UtcDateTime = DateTime()
  %  Timezone = String()
  %  LocalDateTime = DateTime()
  %  DstLocalDateTime = DateTime()
  %  ErrDescr = atom(), unknown_tz
  utc_to_local(UtcDateTime, Timezone) ->
     case lists:keyfind(get_timezone(Timezone), 1, ?tz_database) of
  