File Coverage

blib/lib/DateTimeX/Lite/OlsonDB.pm

Criterion	Covered	Total	%
statement	112	400	28.0
branch	21	182	11.5
condition	3	78	3.8
subroutine	33	73	45.2
pod	0	9	0.0
total	169	742	22.7

package DateTimeX::Lite::OlsonDB;
use strict;
use warnings;
use DateTimeX::Lite;

use vars qw( %MONTHS %DAYS $PLUS_ONE_DAY_DUR $MINUS_ONE_DAY_DUR );

sub DEBUG () { 0 }

my $x = 1;
%MONTHS = map { $_ => $x++ }
          qw( Jan Feb Mar Apr May Jun
	      Jul Aug Sep Oct Nov Dec);

$x = 1;
%DAYS = map { $_ => $x++ }
        qw( Mon Tue Wed Thu Fri Sat Sun );

$PLUS_ONE_DAY_DUR =  DateTimeX::Lite::Duration->new( days => 1 );
$MINUS_ONE_DAY_DUR = DateTimeX::Lite::Duration->new( days => -1 );

sub new
{
    my $class = shift;

    return bless { rules => {},
                   zones => {},
                   links => {},
                 }, $class;
}

sub parse_file {
    my $self = shift;
    my $file = shift;

    open my $fh, "<$file"
        or die "Cannot read $file: $!";

    while (<$fh>) {
        chomp;
        $self->_parse_line($_);
    }
}

sub _parse_line {
    my $self = shift;
    my $line = shift;

    return if $line =~ /^\s+$/;
    return if $line =~ /^#/;

    # remove any comments at the end of the line
    $line =~ s/\s*#.+$//;

    if ( $self->{in_zone} && $line =~ /^\t/ )
    {
        $self->_parse_zone( $line, $self->{in_zone} );
        return;
    }

    foreach ( qw( Rule Zone Link ) )
    {
        if ( substr( $line, 0, 4 ) eq $_ )
        {
            my $m = '_parse_' . lc $_;
            $self->$m($line);
        }
    }
}

sub _parse_rule
{
    my $self = shift;
    my $rule = shift;

    my @items = split /\s+/, $rule, 10;

    shift @items;
    my $name = shift @items;

    my %rule;
    @rule{ qw( from to type in on at save letter ) } = @items;
    delete $rule{letter} if $rule{letter} eq '-';

    # As of the 2003a data, there are no rules with a type set
    delete $rule{type} if $rule{type} eq '-';

    push @{ $self->{rules}{$name} },
        DateTimeX::Lite::OlsonDB::Rule->new( name => $name, %rule );

    undef $self->{in_zone};
}

sub _parse_zone
{
    my $self = shift;
    my $zone = shift;
    my $name = shift;

    my $expect = $name ? 5 : 6;
    my @items = grep { defined && length } split /\s+/, $zone, $expect;

    my %obs;
    unless ($name)
    {
        shift @items; # remove "Zone"
        $name = shift @items;
    }

    @obs{ qw( gmtoff rules format until ) } = @items;

    if ( $obs{rules} =~ /\d\d?:\d\d/ )
    {
        $obs{offset_from_std} = delete $obs{rules};
    }
    else
    {
        delete $obs{rules} if $obs{rules} eq '-';
    }

    delete $obs{until} unless defined $obs{until};

    push @{ $self->{zones}{$name} }, \%obs;

    $self->{in_zone} = $name;
}

sub _parse_link
{
    my $self = shift;
    my $link = shift;

    my @items = split /\s+/, $link, 3;

    $self->{links}{ $items[2] } = $items[1];

    undef $self->{in_zone};
}

sub links { %{ $_[0]->{links} } }

sub zone_names { keys %{ $_[0]->{zones} } }

sub zone
{
    my $self = shift;
    my $name = shift;

    die "Invalid zone name $name"
        unless exists $self->{zones}{$name};

    return
        DateTimeX::Lite::OlsonDB::Zone->new
            ( name => $name,
              observances => $self->{zones}{$name},
              olson_db => $self,
            );
}

sub expanded_zone
{
    my ($self, %p) = @_;

    $p{expand_to_year} ||= (localtime)[5] + 1910;

    my $zone = $self->zone( $p{name} );

    $zone->expand_observances( $self, $p{expand_to_year} );

    return $zone;
}

sub rules_by_name
{
    my $self = shift;
    my $name = shift;

    return unless defined $name;

    die "Invalid rule name $name"
        unless exists $self->{rules}{$name};

    return @{ $self->{rules}{$name} };
}

sub parse_day_spec
{
    my ( $day, $month, $year ) = @_;

    return $day if $day =~ /^\d+$/;

    if ( $day =~ /^last(\w\w\w)$/ )
    {
        my $dow = $DateTimeX::Lite::OlsonDB::DAYS{$1};

        my $last_day = DateTimeX::Lite->last_day_of_month( year  => $year,
                                                    month => $month,
                                                    time_zone => 'floating',
                                                  );

        my $dt =
            DateTimeX::Lite->new( year   => $year,
                           month  => $month,
                           day    => $last_day->day,
                           time_zone => 'floating',
                         );

        while ( $dt->day_of_week != $dow )
        {
            $dt -= $PLUS_ONE_DAY_DUR;
        }

        return $dt->day;
    }
    elsif ( $day =~ /^(\w\w\w)([><])=(\d\d?)$/ )
    {
        my $dow = $DateTimeX::Lite::OlsonDB::DAYS{$1};

        my $dt = DateTimeX::Lite->new( year   => $year,
                                month  => $month,
                                day    => $3,
                                time_zone => 'floating',
                              );

        my $dur = $2 eq '<' ? $MINUS_ONE_DAY_DUR : $PLUS_ONE_DAY_DUR;

        while ( $dt->day_of_week != $dow )
        {
            $dt += $dur;
        }

        return $dt->day;
    }
    else
    {
        die "Invalid on spec for rule: $day\n";
    }
}

sub utc_datetime_for_time_spec {
    my %p = @_;

    # 'w'all - ignore it, because that's the default
    $p{spec} =~ s/w$//;

    # 'g'reenwich, 'u'tc, or 'z'ulu
    my $is_utc = $p{spec} =~ s/[guz]$//;

    # 's'tandard time - ignore DS offset
    my $is_std = $p{spec} =~ s/s$//;

    my ($hour, $minute, $second) = split /:/, $p{spec};
    $minute = 0 unless defined $minute;
    $second = 0 unless defined $second;

    my $add_day = 0;
    if ( $hour == 24 )
    {
        $hour = 0;
        $add_day = 1;
    }

    my $utc;
    if ($is_utc)
    {
        $utc = DateTimeX::Lite->new( year   => $p{year},
                              month  => $p{month},
                              day    => $p{day},
                              hour   => $hour,
                              minute => $minute,
                              second => $second,
                              time_zone => 'floating',
                            );
    }
    else
    {
        my $local = DateTimeX::Lite->new( year   => $p{year},
                                   month  => $p{month},
                                   day    => $p{day},
                                   hour   => $hour,
                                   minute => $minute,
                                   second => $second,
                                   time_zone => 'floating',
                                 );

        $p{offset_from_std} = 0 if $is_std;

        my $dur =
            DateTimeX::Lite::Duration->new
                ( seconds => $p{offset_from_utc} + $p{offset_from_std} );

        $utc = $local - $dur;
    }

    $utc->add( days => 1 ) if $add_day;

    return $utc;
}


package DateTimeX::Lite::OlsonDB::Zone;

use strict;

use DateTimeX::Lite::Util;

sub new
{
    my ($class, %p) = @_;

    my $self = { name => $p{name},
                 observances => $p{observances},
                 changes => [],
                 infinite_rules => {},
               };

    return bless $self, $class;
}

sub name { $_[0]->{name} }

sub expand_observances
{
    my $self = shift;
    my $odb = shift;
    my $max_year = shift;

    my $prev_until;
    for ( my $x = 0; $x < @{ $self->{observances} }; $x++ )
    {
        my %p = %{ $self->{observances}[$x] };
        my $rules_name = delete $p{rules};

        my $last_offset_from_std =
            $self->last_change ? $self->last_change->offset_from_std : 0;
        my $last_offset_from_utc =
            $self->last_change ? $self->last_change->offset_from_utc : 0;

        my $obs =
            DateTimeX::Lite::OlsonDB::Observance->new
                ( %p,
                  utc_start_datetime => $prev_until,
                  rules => [ $odb->rules_by_name($rules_name) ],
                  last_offset_from_utc => $last_offset_from_utc,
                  last_offset_from_std => $last_offset_from_std,
                );

        my $rule = $obs->first_rule;
        my $letter = $rule ? $rule->letter : '';

        my $change =
            DateTimeX::Lite::OlsonDB::Change->new
                ( type => 'observance',
                  utc_start_datetime   => $obs->utc_start_datetime,
                  local_start_datetime => $obs->local_start_datetime,
                  short_name => sprintf( $obs->format, $letter ),
                  observance => $obs,
                  $rule ? ( rule => $rule ) : (),
                );

        if (DateTimeX::Lite::OlsonDB::DEBUG)
        {
            warn "Adding observance change ...\n";

            $change->_debug_output;
        }

        $self->add_change($change);

        if ( $obs->rules )
        {
            $obs->expand_from_rules( $self, $max_year );
        }

        $prev_until =
            $obs->until( $self->last_change ? $self->last_change->offset_from_std : 0 );

        # last observance
        if ( $x == $#{ $self->{observances} } )
        {
            foreach my $rule ( $obs->rules )
            {
                if ( $rule->is_infinite )
                {
                    $self->add_infinite_rule($rule);
                }
            }
        }
    }
}

sub add_change
{
    my $self = shift;
    my $change = shift;

    if ( defined $change->utc_start_datetime )
    {
        if ( @{ $self->{changes} }
             && $self->{changes}[-1]->utc_start_datetime
             && $self->{changes}[-1]->utc_start_datetime == $change->utc_start_datetime
           )
        {
            if ( $self->{changes}[-1]->rule && $change->observance )
            {
                warn " Ignoring previous rule change, that starts the same time as current observance change\n\n"
                    if DateTimeX::Lite::OlsonDB::DEBUG;

                $self->{changes}[-1] = $change;

                return;
            }

            die "Cannot add two different changes that have the same UTC start datetime!\n";
        }

        my $last_change = $self->last_change;

        if ( $last_change->short_name eq $change->short_name
             && $last_change->total_offset == $change->total_offset
             && $last_change->is_dst == $change->is_dst
             && $last_change->observance eq $change->observance
           )
        {
            my $last_rule = $last_change->rule || '';
            my $new_rule = $change->rule || '';

            if ( $last_rule eq $new_rule )
            {
                warn "Skipping identical change\n" if DateTimeX::Lite::OlsonDB::DEBUG;

                return;
            }
        }

        push @{ $self->{changes} }, $change;
    }
    else
    {
        if ( $self->{earliest} )
        {
            die "There can only be one earliest time zone change!";
        }
        else
        {
            $self->{earliest} = $change;
        }
    }
}

sub add_infinite_rule
{
    $_[0]->{infinite_rules}{ $_[1] } = $_[1];
}

sub last_change { return unless @{ $_[0]->{changes} } || $_[0]->{earliest};
                  return ( @{ $_[0]->{changes} } ?
                           $_[0]->{changes}[-1] :
                           $_[0]->{earliest} ); }

sub sorted_changes { ( ( defined $_[0]->{earliest} ? $_[0]->{earliest} : () ),
                       sort { $a->utc_start_datetime <=> $b->utc_start_datetime }
                       @{ $_[0]->{changes} } ) }

sub infinite_rules { values %{ $_[0]->{infinite_rules} } }


package DateTimeX::Lite::OlsonDB::Observance;

use strict;

use DateTimeX::Lite::Util;

sub new
{
    my ($class, %p) = @_;

    $p{until} ||= '';
    $p{offset_from_std} ||= 0;
    $p{last_offset_from_utc} ||= 0;
    $p{last_offset_from_std} ||= 0;

    my $offset_from_utc = DateTimeX::Lite::Util::offset_as_seconds( $p{gmtoff} );
    my $offset_from_std = DateTimeX::Lite::Util::offset_as_seconds( $p{offset_from_std} );

    my $last_offset_from_utc = delete $p{last_offset_from_utc};
    my $last_offset_from_std = delete $p{last_offset_from_std};

    my $self = bless { %p,
                       offset_from_utc => $offset_from_utc,
                       offset_from_std => $offset_from_std,
                       until => [ split /\s+/, $p{until} ],
                     }, $class;

    my $local_start_datetime;
    if ( $p{utc_start_datetime} )
    {
        $self->{first_rule} =
            $self->_first_rule( $last_offset_from_utc, $last_offset_from_std );

        $offset_from_std += $self->{first_rule}->offset_from_std if $self->{first_rule};

        $local_start_datetime = $p{utc_start_datetime}->clone;

        $local_start_datetime +=
            DateTimeX::Lite::Duration->new( seconds => $offset_from_utc + $offset_from_std );

        $self->{local_start_datetime} = $local_start_datetime;
    }

    return $self;
}

sub offset_from_utc { $_[0]->{offset_from_utc} }
sub offset_from_std { $_[0]->{offset_from_std} }
sub total_offset { $_[0]->offset_from_utc + $_[0]->offset_from_std }

sub rules { @{ $_[0]->{rules} } }
sub first_rule { $_[0]->{first_rule} }

sub format { $_[0]->{format} }

sub utc_start_datetime   { $_[0]->{utc_start_datetime} }
sub local_start_datetime { $_[0]->{local_start_datetime} }

sub expand_from_rules
{
    my $self = shift;
    my $zone = shift;
    # real max is year + 1 so we include max year
    my $max_year = (shift) + 1;

    my $min_year;

    if ( $self->utc_start_datetime )
    {
        $min_year = $self->utc_start_datetime->year;
    }
    else
    {
        # There is at least one time zone that has an infinite
        # observance, but that observance has rules that only start at
        # a certain point - Pacific/Chatham

        # In this case we just find the earliest rule and start there

        $min_year = ( sort { $a <=> $b } map { $_->min_year } $self->rules )[0];
    }

    my $until = $self->until( $zone->last_change->offset_from_std );
    if ($until)
    {
        $max_year = $until->year;
    }
    else
    {
        # Some zones, like Asia/Tehran, have a predefined fixed set of
        # rules that go well into the future (2037 for Asia/Tehran)
        my $max_rule_year = 0;
        foreach my $rule ( $self->rules )
        {
            $max_rule_year = $rule->max_year
                if $rule->max_year && $rule->max_year > $max_rule_year;
        }

        $max_year = $max_rule_year if $max_rule_year > $max_year;
    }

    foreach my $year ( $min_year .. $max_year )
    {
        my @rules = $self->_sorted_rules_for_year($year);

        foreach my $rule (@rules)
        {
            my $dt =
                $rule->utc_start_datetime_for_year
                    ( $year, $self->offset_from_utc, $zone->last_change->offset_from_std );

            next if $self->utc_start_datetime && $dt <= $self->utc_start_datetime;

            my $until = $self->until( $zone->last_change->offset_from_std );

            next if $until && $dt >= $until;

            my $change =
                DateTimeX::Lite::OlsonDB::Change->new
                    ( type => 'rule',
                      utc_start_datetime   => $dt,
                      local_start_datetime =>
                      $dt +
                      DateTimeX::Lite::Duration->new
                          ( seconds => $self->total_offset + $rule->offset_from_std ),
                      short_name => sprintf( $self->{format}, $rule->letter ),
                      observance => $self,
                      rule       => $rule,
                    );

            if (DateTimeX::Lite::OlsonDB::DEBUG)
            {
                warn "Adding rule change ...\n";

                $change->_debug_output;
            }

            $zone->add_change($change);
        }
    }
}

sub _sorted_rules_for_year
{
    my $self = shift;
    my $year = shift;

    return
        ( map { $_->[0] }
          sort { $a->[1] <=> $b->[1] }
          map { my $dt = $_->utc_start_datetime_for_year( $year, $self->offset_from_utc, 0 );
                [ $_, $dt ] }
          grep { $_->min_year <= $year && ( ( ! $_->max_year ) || $_->max_year >= $year ) }
          $self->rules
        );
}

sub until
{
    my $self = shift;
    my $offset_from_std = shift || $self->offset_from_std;

    return unless defined $self->until_year;

    my $utc =
        DateTimeX::Lite::OlsonDB::utc_datetime_for_time_spec
                ( spec  => $self->until_time_spec,
                  year  => $self->until_year,
                  month => $self->until_month,
                  day   => $self->until_day,
                  offset_from_utc => $self->offset_from_utc,
                  offset_from_std => $offset_from_std,
                );

    return $utc;
}

sub until_year { $_[0]->{until}[0] }

sub until_month
{
    ( defined $_[0]->{until}[1] ?
      $DateTimeX::Lite::OlsonDB::MONTHS{ $_[0]->{until}[1] } :
      1
    );
}

sub until_day
{
    ( defined $_[0]->{until}[2]
      ? DateTimeX::Lite::OlsonDB::parse_day_spec
            ( $_[0]->{until}[2], $_[0]->until_month, $_[0]->until_year )
      : 1
    );
}

sub until_time_spec
{
    defined $_[0]->{until}[3] ? $_[0]->{until}[3] : '00:00:00';
}

sub _first_rule
{
    my $self = shift;
    my $last_offset_from_utc = shift;
    my $last_offset_from_std = shift;

    return unless $self->utc_start_datetime;
    return unless $self->rules;

    my $date = $self->utc_start_datetime;

    my @rules = $self->rules;

    my %possible_rules;

    my $year = $date->year;
    foreach my $rule (@rules)
    {
        # We need to look at what the year _would_ be if we added the
        # rule's offset to the UTC date.  Otherwise we can end up with
        # a UTC date in year X, and a rule that starts in _local_ year
        # X + 1, where that rule really does apply to that UTC date.
        my $temp_year =
            $date->clone->add
                ( seconds => $self->offset_from_utc + $rule->offset_from_std )->year;

        # Save the highest value
        $year = $temp_year if $temp_year > $year;

        next if $rule->min_year > $temp_year;

        $possible_rules{$rule} = $rule;
    }

    return unless keys %possible_rules;

    my $earliest_year = $year - 1;
    foreach my $rule (@rules)
    {
        $earliest_year = $rule->min_year
            if $rule->min_year < $earliest_year;
    }

    # figure out what date each rule would start on _if_ that rule
    # were applied to this current observance.  this could be a rule
    # that started much earlier, but is only now active because of an
    # observance switch.  An obnoxious example of this is
    # America/Phoenix in 1944, which applies the US rule in April,
    # thus (re-)instating the "war time" rule from 1942.  Can you say
    # ridiculous crack-smoking stupidity?
    my @rule_dates;
    foreach my $y ( $earliest_year .. $year )
    {
      RULE:
        foreach my $rule ( values %possible_rules )
        {
            # skip rules that can't have applied the year before the
            # observance started.
            if ( $rule->min_year > $y )
            {
                warn "Skipping rule beginning in ", $rule->min_year, ".  Year is $y.\n"
                    if DateTimeX::Lite::OlsonDB::DEBUG;

                next RULE;
            }

            if ( $rule->max_year && $rule->max_year < $y )
            {
                warn "Skipping rule ending in ", $rule->max_year, ".     Year is $y.\n"
                    if DateTimeX::Lite::OlsonDB::DEBUG;

                next RULE;
            }

            my $rule_start =
                $rule->utc_start_datetime_for_year
                    ( $y, $last_offset_from_utc, $last_offset_from_std );

            push @rule_dates, [ $rule_start, $rule ];
        }
    }

    return unless @rule_dates;

    @rule_dates = sort { $a->[0] <=> $b->[0] } @rule_dates;

    warn "Looking for first rule ...\n" if DateTimeX::Lite::OlsonDB::DEBUG;
    warn " Observance starts: ", $date->datetime, "\n\n"
        if DateTimeX::Lite::OlsonDB::DEBUG;

    # ... look through the rules to see if any are still in
    # effect at the beginning of the observance
    for ( my $x = 0; $x < @rule_dates; $x++ )
    {
        my ( $dt, $rule ) = @{ $rule_dates[$x] };
        my ( $next_dt, $next_rule ) =
            $x < @rule_dates - 1 ? @{ $rule_dates[ $x + 1 ] } : undef;

        next if $next_dt && $next_dt < $date;

        warn " This rule starts:  ", $dt->datetime, "\n"
            if DateTimeX::Lite::OlsonDB::DEBUG;

        warn " Next rule starts:  ", $next_dt->datetime, "\n"
            if $next_dt && DateTimeX::Lite::OlsonDB::DEBUG;

        warn " No next rule\n\n"
            if ! $next_dt && DateTimeX::Lite::OlsonDB::DEBUG;

        if ( $dt <= $date )
        {
            if ($next_dt)
            {
                return $rule if $date < $next_dt;
                return $next_rule if $date == $next_dt;
            }
            else
            {
                return $rule;
            }
        }
    }

    return;
}


package DateTimeX::Lite::OlsonDB::Rule;

use strict;

use DateTimeX::Lite::Util;
use DateTimeX::Lite::Duration;

sub new
{
    my ($class, %p) = @_;
    $p{type} ||= undef;
    $p{letter} ||= '';

    my $save = $p{save};

    if ($save)
    {
        $p{offset_from_std} = DateTimeX::Lite::Util::offset_as_seconds($save);
    }
    else
    {
        $p{offset_from_std} = 0;
    }

    return bless \%p, $class;
}

sub name { $_[0]->{name} }
sub offset_from_std { $_[0]->{offset_from_std} }
sub letter { $_[0]->{letter} }
sub min_year { $_[0]->{from} }

sub max_year { $_[0]->{to} eq 'only' ? $_[0]->min_year :
               $_[0]->{to} eq 'max' ? undef : $_[0]->{to} }

sub is_infinite { $_[0]->{to} eq 'max' ? 1 : 0 }

sub month { $DateTimeX::Lite::OlsonDB::MONTHS{ $_[0]->{in} } }
sub on { $_[0]->{on} }
sub at { $_[0]->{at} }

sub utc_start_datetime_for_year
{
    my $self   = shift;
    my $year   = shift;
    my $offset_from_utc = shift;
    # should be the offset of the _previous_ rule
    my $offset_from_std = shift;

    my $day =
        DateTimeX::Lite::OlsonDB::parse_day_spec( $self->on, $self->month, $year );

    my $utc =
        DateTimeX::Lite::OlsonDB::utc_datetime_for_time_spec
                ( spec  => $self->at,
                  year  => $year,
                  month => $self->month,
                  day   => $day,
                  offset_from_utc => $offset_from_utc,
                  offset_from_std => $offset_from_std,
                );

    return $utc;
}


package DateTimeX::Lite::OlsonDB::Change;

use strict;

sub new
{
    my ($class, %p) = @_;
    $p{rule} ||= undef;
    if ($p{type} !~ /^(?:observance|rule)$/ ) {
        die "whoa $p{type}";
    }

    # These are almost always mutually exclusive, except when adding
    # an observance change and the last rule has no offset, but the
    # new observance has an anonymous rule.  In that case, prefer the
    # offset from std defined in the observance to that in the
    # previous rule (what a mess!).
    if ( $p{type} eq 'observance' )
    {
        $p{offset_from_std} = $p{rule}->offset_from_std if defined $p{rule};
        $p{offset_from_std} = $p{observance}->offset_from_std
            if $p{observance}->offset_from_std;
        $p{offset_from_std} ||= 0;
    }
    else
    {
        $p{offset_from_std} = $p{observance}->offset_from_std;
        $p{offset_from_std} = $p{rule}->offset_from_std if defined $p{rule};
    }

    $p{offset_from_utc} = $p{observance}->offset_from_utc;

    $p{is_dst} = 0;
    $p{is_dst} = 1 if $p{rule} && $p{rule}->offset_from_std;
    $p{is_dst} = 1 if $p{observance}->offset_from_std;

    if ( $p{short_name} =~ m{(\w+)/(\w+)} )
    {
        $p{short_name} = $p{is_dst} ? $2 : $1;
    }

    return bless \%p, $class;
}

sub utc_start_datetime   { $_[0]->{utc_start_datetime} }
sub local_start_datetime { $_[0]->{local_start_datetime} }
sub short_name { $_[0]->{short_name} }
sub is_dst     { $_[0]->{is_dst} }
sub observance { $_[0]->{observance} }
sub rule       { $_[0]->{rule} }
sub offset_from_utc { $_[0]->{offset_from_utc} }
sub offset_from_std { $_[0]->{offset_from_std} }
sub total_offset { $_[0]->offset_from_utc + $_[0]->offset_from_std }

sub two_changes_as_span
{
    my ( $c1, $c2, $last_total_offset ) = @_;

    my ( $utc_start, $local_start );

    if ( defined $c1->utc_start_datetime )
    {
        $utc_start = $c1->utc_start_datetime->utc_rd_as_seconds;
        $local_start = $c1->local_start_datetime->utc_rd_as_seconds;
    }
    else
    {
        $utc_start = $local_start = '-inf';
    }

    my $utc_end = $c2->utc_start_datetime->utc_rd_as_seconds;
    my $local_end = $utc_end + $c1->total_offset;

    return { utc_start   => $utc_start,
             utc_end     => $utc_end,
             local_start => $local_start,
             local_end   => $local_end,
             short_name  => $c1->short_name,
             offset      => $c1->total_offset,
             is_dst      => $c1->is_dst,
           };
}

sub _debug_output
{
    my $self = shift;

    my $obs = $self->observance;

    if ( $self->utc_start_datetime )
    {
        warn " UTC:        ", $self->utc_start_datetime->datetime, "\n";
        warn " Local:      ", $self->local_start_datetime->datetime, "\n";
    }
    else
    {
        warn " First change (starts at -inf)\n";
    }

    warn " Short name: ", $self->short_name, "\n";
    warn " UTC offset: ", $obs->offset_from_utc, "\n";

    if ( $obs->offset_from_std || $self->rule )
    {
        if ( $obs->offset_from_std )
        {
            warn " Std offset: ", $obs->offset_from_std, "\n";
        }

        if ( $self->rule )
        {
            warn " Std offset: ", $self->rule->offset_from_std, ' - ',
                 $self->rule->name, " rule\n";
        }
    }
    else
    {
        warn " Std offset: 0 - no rule\n";
    }

    warn "\n";
}

1;

__END__