package DateTime::TimeZone;

use 5.008004;

use strict;
use warnings;
use namespace::autoclean;

our $VERSION = '2.67';

# Note that while we make use of DateTime::Duration in this module if we
# actually try to load it here all hell breaks loose with circular
# dependencies.
use DateTime::TimeZone::Catalog;
use DateTime::TimeZone::Floating;
use DateTime::TimeZone::Local;
use DateTime::TimeZone::OffsetOnly;
use DateTime::TimeZone::OlsonDB::Change;
use DateTime::TimeZone::UTC;
use Module::Runtime qw( require_module );
use Params::ValidationCompiler 0.13 qw( validation_for );
use Specio::Library::Builtins;
use Specio::Library::String;
use Try::Tiny;

## no critic (ValuesAndExpressions::ProhibitConstantPragma)
use constant INFINITY     => 100**1000;
use constant NEG_INFINITY => -1 * ( 100**1000 );

# the offsets for each span element
use constant UTC_START   => 0;
use constant UTC_END     => 1;
use constant LOCAL_START => 2;
use constant LOCAL_END   => 3;
use constant OFFSET      => 4;
use constant IS_DST      => 5;
use constant SHORT_NAME  => 6;

my %SpecialName = map { $_ => 1 }
    qw( EST MST HST CET EET MET WET EST5EDT CST6CDT MST7MDT PST8PDT );

{
    my $validator = validation_for(
        name             => '_check_new_params',
        name_is_optional => 1,
        params           => {
            name => {
                type => t('NonEmptyStr'),
            },
        },
    );

    sub new {
        shift;
        my %p = $validator->(@_);

        if ( exists $DateTime::TimeZone::Catalog::LINKS{ $p{name} } ) {
            $p{name} = $DateTime::TimeZone::Catalog::LINKS{ $p{name} };
        }
        elsif ( exists $DateTime::TimeZone::Catalog::LINKS{ uc $p{name} } ) {
            $p{name} = $DateTime::TimeZone::Catalog::LINKS{ uc $p{name} };
        }

        unless ( $p{name} =~ m{/}
            || $SpecialName{ $p{name} } ) {
            if ( $p{name} eq 'floating' ) {
                return DateTime::TimeZone::Floating->instance;
            }

            if ( $p{name} eq 'local' ) {
                return DateTime::TimeZone::Local->TimeZone();
            }

            if ( $p{name} eq 'UTC' || $p{name} eq 'Z' ) {
                return DateTime::TimeZone::UTC->instance;
            }

            return DateTime::TimeZone::OffsetOnly->new( offset => $p{name} );
        }

        if ( $p{name} =~ m{Etc/(?:GMT|UTC)(\+|-)(\d{1,2})}i ) {

            # Etc/GMT+4 is actually UTC-4. For more info, see
            # https://data.iana.org/time-zones/tzdb/etcetera
            my $sign  = $1 eq '-' ? '+' : '-';
            my $hours = $2;
            die "The timezone '$p{name}' is an invalid name.\n"
                unless $hours <= 14;
            return DateTime::TimeZone::OffsetOnly->new(
                offset => "${sign}${hours}:00" );
        }

        my $subclass = $p{name};
        $subclass =~ s{/}{::}g;
        $subclass =~ s/-(\d)/_Minus$1/;
        $subclass =~ s/\+/_Plus/;
        $subclass =~ s/-/_/g;

        my $real_class = "DateTime::TimeZone::$subclass";

        die "The timezone '$p{name}' is an invalid name.\n"
            unless $real_class =~ /^\w+(::\w+)*$/;

        unless ( $real_class->can('instance') ) {
            ($real_class)
                = $real_class =~ m{\A([a-zA-Z0-9_]+(?:::[a-zA-Z0-9_]+)*)\z};

            my $e;
            try {
                ## no critic (Variables::RequireInitializationForLocalVars)
                local $SIG{__DIE__};
                require_module($real_class);
            }
            catch {
                $e = $_;
            };

            if ($e) {
                my $regex = join '.', split /::/, $real_class;
                $regex .= '\\.pm';

                if ( $e =~ /^Can't locate $regex/i ) {
                    die
                        "The timezone '$p{name}' could not be loaded, or is an invalid name.\n";
                }
                else {
                    die $e;
                }
            }
        }

        my $zone = $real_class->instance( name => $p{name}, is_olson => 1 );

        if ( $zone->is_olson() ) {
            my $object_version
                = $zone->can('olson_version')
                ? $zone->olson_version()
                : 'unknown';
            my $catalog_version = DateTime::TimeZone::Catalog->OlsonVersion();

            if ( $object_version ne $catalog_version ) {
                warn
                    "Loaded $real_class, which is from a different version ($object_version) of the Olson database than this installation of DateTime::TimeZone ($catalog_version).\n";
            }
        }

        return $zone;
    }
}

{
    my $validator = validation_for(
        name             => '_check_init_params',
        name_is_optional => 1,
        params           => {
            name => {
                type => t('NonEmptyStr'),
            },
            spans => {
                type => t('ArrayRef'),
            },
            is_olson => {
                type    => t('Bool'),
                default => 0,
            },
        },
    );

    ## no critic (Subroutines::ProhibitUnusedPrivateSubroutines)
    sub _init {
        my $class = shift;
        my %p     = $validator->(@_);

        my $self = bless {
            name     => $p{name},
            spans    => $p{spans},
            is_olson => $p{is_olson},
        }, $class;

        foreach my $k (qw( last_offset last_observance rules max_year )) {
            my $m = "_$k";
            $self->{$k} = $self->$m() if $self->can($m);
        }

        return $self;
    }
    ## use critic
}

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

sub is_dst_for_datetime {
    my $self = shift;

    my $span = $self->_span_for_datetime( 'utc', $_[0] );

    return $span->[IS_DST];
}

sub offset_for_datetime {
    my $self = shift;

    my $span = $self->_span_for_datetime( 'utc', $_[0] );

    return $span->[OFFSET];
}

sub offset_for_local_datetime {
    my $self = shift;

    my $span = $self->_span_for_datetime( 'local', $_[0] );

    return $span->[OFFSET];
}

sub short_name_for_datetime {
    my $self = shift;

    my $span = $self->_span_for_datetime( 'utc', $_[0] );

    return $span->[SHORT_NAME];
}

sub _span_for_datetime {
    my $self = shift;
    my $type = shift;
    my $dt   = shift;

    my $method = $type . '_rd_as_seconds';

    my $end = $type eq 'utc' ? UTC_END : LOCAL_END;

    my $span;
    my $seconds = $dt->$method();
    if ( $seconds < $self->max_span->[$end] ) {
        $span = $self->_spans_binary_search( $type, $seconds );
    }
    else {
        my $until_year = $dt->utc_year + 1;
        $span = $self->_generate_spans_until_match(
            $until_year, $seconds,
            $type
        );
    }

    # This means someone gave a local time that doesn't exist
    # (like during a transition into savings time)
    unless ( defined $span ) {
        my $err = 'Invalid local time for date';
        $err .= q{ } . $dt->iso8601 if $type eq 'utc';
        $err .= ' in time zone: ' . $self->name;
        $err .= "\n";

        die $err;
    }

    return $span;
}

sub _spans_binary_search {
    my $self = shift;
    my ( $type, $seconds ) = @_;

    my ( $start, $end ) = _keys_for_type($type);

    my $min = 0;
    my $max = scalar @{ $self->{spans} } + 1;
    my $i   = int( $max / 2 );

    # special case for when there are only 2 spans
    $i++ if $max % 2 && $max != 3;

    $i = 0 if @{ $self->{spans} } == 1;

    while (1) {
        my $current = $self->{spans}[$i];

        if ( $seconds < $current->[$start] ) {
            $max = $i;
            my $c = int( ( $i - $min ) / 2 );
            $c ||= 1;

            $i -= $c;

            return if $i < $min;
        }
        elsif ( $seconds >= $current->[$end] ) {
            $min = $i;
            my $c = int( ( $max - $i ) / 2 );
            $c ||= 1;

            $i += $c;

            return if $i >= $max;
        }
        else {

            # Special case for overlapping ranges because of DST and
            # other weirdness (like Alaska's change when bought from
            # Russia by the US).  Always prefer latest span.
            if ( $current->[IS_DST] && $type eq 'local' ) {

                # Asia/Dhaka in 2009j goes into DST without any known
                # end-of-DST date (wtf, Bangladesh).
                return $current if $current->[UTC_END] == INFINITY;

                my $next = $self->{spans}[ $i + 1 ];

                # Sometimes we will get here and the span we're
                # looking at is the last that's been generated so far.
                # We need to try to generate one more or else we run
                # out.
                $next ||= $self->_generate_next_span;

                die "No next span in $self->{max_year}" unless defined $next;

                if (   ( !$next->[IS_DST] )
                    && $next->[$start] <= $seconds
                    && $seconds <= $next->[$end] ) {
                    return $next;
                }
            }

            return $current;
        }
    }
}

sub _generate_next_span {
    my $self = shift;

    my $last_idx = $#{ $self->{spans} };

    my $max_span = $self->max_span;

    # Kind of a hack, but AFAIK there are no zones where it takes
    # _more_ than a year for a _future_ time zone change to occur, so
    # by looking two years out we can ensure that we will find at
    # least one more span.  Of course, I will no doubt be proved wrong
    # and this will cause errors.
    $self->_generate_spans_until_match(
        $self->{max_year} + 2,
        $max_span->[UTC_END] + ( 366 * 86400 ), 'utc'
    );

    return $self->{spans}[ $last_idx + 1 ];
}

sub _generate_spans_until_match {
    my $self                = shift;
    my $generate_until_year = shift;
    my $seconds             = shift;
    my $type                = shift;

    my @changes;
    my @rules = @{ $self->_rules };
    foreach my $year ( $self->{max_year} .. $generate_until_year ) {
        ## no critic (ControlStructures::ProhibitCStyleForLoops)
        for ( my $x = 0; $x < @rules; $x++ ) {
            my $last_offset_from_std;

            if ( @rules == 2 ) {
                $last_offset_from_std
                    = $x
                    ? $rules[0]->offset_from_std
                    : $rules[1]->offset_from_std;
            }
            elsif ( @rules == 1 ) {
                $last_offset_from_std = $rules[0]->offset_from_std;
            }
            else {
                my $count = scalar @rules;
                die
                    "Cannot generate future changes for zone with $count infinite rules\n";
            }

            my $rule = $rules[$x];

            my $next = $rule->utc_start_datetime_for_year(
                $year,
                $self->{last_offset}, $last_offset_from_std
            );

            # don't bother with changes we've seen already
            next if $next->utc_rd_as_seconds < $self->max_span->[UTC_END];

            push @changes,
                DateTime::TimeZone::OlsonDB::Change->new(
                type                 => 'rule',
                utc_start_datetime   => $next,
                local_start_datetime => $next + DateTime::Duration->new(
                    seconds => $self->{last_observance}->total_offset
                        + $rule->offset_from_std
                ),
                short_name => $self->{last_observance}
                    ->formatted_short_name( $rule->letter, $rule ),
                observance => $self->{last_observance},
                rule       => $rule,
                );
        }
    }

    $self->{max_year} = $generate_until_year;

    my @sorted
        = sort { $a->utc_start_datetime <=> $b->utc_start_datetime } @changes;

    my ( $start, $end ) = _keys_for_type($type);

    my $match;
    ## no critic (ControlStructures::ProhibitCStyleForLoops)
    for ( my $x = 1; $x < @sorted; $x++ ) {
        my $span = DateTime::TimeZone::OlsonDB::Change::two_changes_as_span(
            @sorted[ $x - 1, $x ] );

        $span = _span_as_array($span);

        push @{ $self->{spans} }, $span;

        $match = $span
            if $seconds >= $span->[$start] && $seconds < $span->[$end];
    }

    return $match;
}

sub max_span { $_[0]->{spans}[-1] }

sub _keys_for_type {
    $_[0] eq 'utc' ? ( UTC_START, UTC_END ) : ( LOCAL_START, LOCAL_END );
}

sub _span_as_array {
    [
        @{ $_[0] }{
            qw( utc_start utc_end local_start local_end offset is_dst short_name )
        }
    ];
}

sub is_floating {0}

sub is_utc {0}

sub has_dst_changes {0}

sub name     { $_[0]->{name} }
sub category { ( split /\//, $_[0]->{name}, 2 )[0] }

sub is_valid_name {
    my $class = shift;
    my $name  = shift;

    my $tz = try {
        ## no critic (Variables::RequireInitializationForLocalVars)
        local $SIG{__DIE__};
        $class->new( name => $name );
    };

    return $tz && $tz->isa('DateTime::TimeZone') ? 1 : 0;
}

sub STORABLE_freeze {
    my $self = shift;

    return $self->name;
}

sub STORABLE_thaw {
    my $self = shift;
    shift;
    my $serialized = shift;

    my $class = ref $self || $self;

    my $obj;
    if ( $class->isa(__PACKAGE__) ) {
        $obj = __PACKAGE__->new( name => $serialized );
    }
    else {
        $obj = $class->new( name => $serialized );
    }

    %$self = %$obj;

    return $self;
}

#
# Functions
#
sub offset_as_seconds {
    my $offset = shift;
    $offset = shift if try {
        ## no critic (Variables::RequireInitializationForLocalVars)
        local $SIG{__DIE__};
        $offset->isa('DateTime::TimeZone');
    };

    return undef unless defined $offset;

    return 0 if $offset eq '0';

    my ( $sign, $hours, $minutes, $seconds );
    if ( $offset =~ /^([\+\-])?(\d\d?):(\d\d)(?::(\d\d))?$/ ) {
        ( $sign, $hours, $minutes, $seconds ) = ( $1, $2, $3, $4 );
    }
    elsif ( $offset =~ /^([\+\-])?(\d\d)(\d\d)(\d\d)?$/ ) {
        ( $sign, $hours, $minutes, $seconds ) = ( $1, $2, $3, $4 );
    }
    else {
        return undef;
    }

    $sign = '+'  unless defined $sign;
    return undef unless $hours >= 0   && $hours <= 99;
    return undef unless $minutes >= 0 && $minutes <= 59;
    return undef
        unless !defined($seconds) || ( $seconds >= 0 && $seconds <= 59 );

    my $total = $hours * 3600 + $minutes * 60;
    $total += $seconds if $seconds;
    $total *= -1       if $sign eq '-';

    return $total;
}

sub offset_as_string {
    my $offset = shift;
    $offset = shift if try {
        ## no critic (Variables::RequireInitializationForLocalVars)
        local $SIG{__DIE__};
        $offset->isa('DateTime::TimeZone');
    };
    my $sep = shift || q{};

    return undef unless defined $offset;
    return undef unless $offset >= -359999 && $offset <= 359999;

    my $sign = $offset < 0 ? '-' : '+';

    $offset = abs($offset);

    my $hours = int( $offset / 3600 );
    $offset %= 3600;
    my $mins = int( $offset / 60 );
    $offset %= 60;
    my $secs = int($offset);

    return (
        $secs
        ? sprintf(
            '%s%02d%s%02d%s%02d', $sign, $hours, $sep, $mins, $sep, $secs
            )
        : sprintf( '%s%02d%s%02d', $sign, $hours, $sep, $mins )
    );
}

# These methods all operate on data contained in the DateTime/TimeZone/Catalog.pm file.

sub all_names {
    return wantarray
        ? @DateTime::TimeZone::Catalog::ALL
        : [@DateTime::TimeZone::Catalog::ALL];
}

sub categories {
    return wantarray
        ? @DateTime::TimeZone::Catalog::CATEGORY_NAMES
        : [@DateTime::TimeZone::Catalog::CATEGORY_NAMES];
}

sub links {
    return wantarray
        ? %DateTime::TimeZone::Catalog::LINKS
        : {%DateTime::TimeZone::Catalog::LINKS};
}

sub names_in_category {
    shift if $_[0]->isa('DateTime::TimeZone');
    return unless exists $DateTime::TimeZone::Catalog::CATEGORIES{ $_[0] };

    return wantarray
        ? @{ $DateTime::TimeZone::Catalog::CATEGORIES{ $_[0] } }
        : $DateTime::TimeZone::Catalog::CATEGORIES{ $_[0] };
}

sub countries {
    wantarray
        ? ( sort keys %DateTime::TimeZone::Catalog::ZONES_BY_COUNTRY )
        : [ sort keys %DateTime::TimeZone::Catalog::ZONES_BY_COUNTRY ];
}

sub names_in_country {
    shift if $_[0]->isa('DateTime::TimeZone');

    return
        unless
        exists $DateTime::TimeZone::Catalog::ZONES_BY_COUNTRY{ lc $_[0] };

    return
        wantarray
        ? @{ $DateTime::TimeZone::Catalog::ZONES_BY_COUNTRY{ lc $_[0] } }
        : $DateTime::TimeZone::Catalog::ZONES_BY_COUNTRY{ lc $_[0] };
}

1;

# ABSTRACT: Time zone object base class and factory

__END__

=pod

=encoding UTF-8

=head1 NAME

DateTime::TimeZone - Time zone object base class and factory

=head1 VERSION

version 2.67

=head1 SYNOPSIS

  use DateTime;
  use DateTime::TimeZone;

  my $tz = DateTime::TimeZone->new( name => 'America/Chicago' );

  my $dt = DateTime->now();
  my $offset = $tz->offset_for_datetime($dt);

=head1 DESCRIPTION

This class is the base class for all time zone objects.  A time zone is
represented internally as a set of observances, each of which describes the
offset from GMT for a given time period.

Note that without the L<DateTime> module, this module does not do much.  It's
primary interface is through a L<DateTime> object, and most users will not need
to directly use C<DateTime::TimeZone> methods.

=head2 Special Case Platforms

If you are on the Win32 platform, you will want to also install
L<DateTime::TimeZone::Local::Win32>. This will enable you to specify a time
zone of C<'local'> when creating a L<DateTime> object.

If you are on HPUX, install L<DateTime::TimeZone::HPUX>. This provides support
for HPUX style time zones like C<'MET-1METDST'>.

=head1 USAGE

This class has the following methods:

=head2 DateTime::TimeZone->new( name => $tz_name )

Given a valid time zone name, this method returns a new time zone blessed into
the appropriate subclass.  Subclasses are named for the given time zone, so
that the time zone "America/Chicago" is the
DateTime::TimeZone::America::Chicago class.

If the name given is a "link" name in the Olson database, the object created
may have a different name.  For example, there is a link from the old "EST5EDT"
name to "America/New_York".

When loading a time zone from the Olson database, the constructor checks the
version of the loaded class to make sure it matches the version of the current
DateTime::TimeZone installation. If they do not match it will issue a warning.
This is useful because time zone names may fall out of use, but you may have an
old module file installed for that time zone.

There are also several special values that can be given as names.

If the "name" parameter is "floating", then a C<DateTime::TimeZone::Floating>
object is returned.  A floating time zone does not have I<any> offset, and is
always the same time.  This is useful for calendaring applications, which may
need to specify that a given event happens at the same I<local> time,
regardless of where it occurs. See L<RFC
2445|https://www.ietf.org/rfc/rfc2445.txt> for more details.

If the "name" parameter is "UTC", then a C<DateTime::TimeZone::UTC> object is
returned.

If the "name" is an offset string, it is converted to a number, and a
C<DateTime::TimeZone::OffsetOnly> object is returned.

=head3 The "local" time zone

If the "name" parameter is "local", then the module attempts to determine the
local time zone for the system.

The method for finding the local zone varies by operating system. See the
appropriate module for details of how we check for the local time zone.

=over 4

=item * L<DateTime::TimeZone::Local::Unix>

=item * L<DateTime::TimeZone::Local::Android>

=item * L<DateTime::TimeZone::Local::hpux>

=item * L<DateTime::TimeZone::Local::Win32>

=item * L<DateTime::TimeZone::Local::VMS>

=back

If a local time zone is not found, then an exception will be thrown. This
exception will always stringify to something containing the text C<"Cannot
determine local time zone">.

If you are writing code for users to run on systems you do not control, you
should try to account for the possibility that this exception may be thrown.
Falling back to UTC might be a reasonable alternative.

When writing tests for your modules that might be run on others' systems, you
are strongly encouraged to either not use C<local> when creating L<DateTime>
objects or to set C<$ENV{TZ}> to a known value in your test code. All of the
per-OS classes check this environment variable.

=head2 $tz->offset_for_datetime( $dt )

Given a C<DateTime> object, this method returns the offset in seconds for the
given datetime.  This takes into account historical time zone information, as
well as Daylight Saving Time.  The offset is determined by looking at the
object's UTC Rata Die days and seconds.

=head2 $tz->offset_for_local_datetime( $dt )

Given a C<DateTime> object, this method returns the offset in seconds for the
given datetime.  Unlike the previous method, this method uses the local time's
Rata Die days and seconds.  This should only be done when the corresponding UTC
time is not yet known, because local times can be ambiguous due to Daylight
Saving Time rules.

=head2 $tz->is_dst_for_datetime( $dt )

Given a C<DateTime> object, this method returns true if the DateTime is
currently in Daylight Saving Time.

=head2 $tz->name

Returns the name of the time zone.

=head2 $tz->short_name_for_datetime( $dt )

Given a C<DateTime> object, this method returns the "short name" for the
current observance and rule this datetime is in.  These are names like "EST",
"GMT", etc.

It is B<strongly> recommended that you do not rely on these names for anything
other than display.  These names are not official, and many of them are simply
the invention of the Olson database maintainers. Moreover, these names are not
unique.  For example, there is an "EST" at both -0500 and +1000/+1100.

=head2 $tz->is_floating

Returns a boolean indicating whether or not this object represents a floating
time zone, as defined by L<RFC 2445|https://www.ietf.org/rfc/rfc2445.txt>.

=head2 $tz->is_utc

Indicates whether or not this object represents the UTC (GMT) time zone.

=head2 $tz->has_dst_changes

Indicates whether or not this zone has I<ever> had a change to and from DST,
either in the past or future.

=head2 $tz->is_olson

Returns true if the time zone is a named time zone from the Olson database.

=head2 $tz->category

Returns the part of the time zone name before the first slash.  For example,
the "America/Chicago" time zone would return "America".

=head2 DateTime::TimeZone->is_valid_name($name)

Given a string, this method returns a boolean value indicating whether or not
the string is a valid time zone name.  If you are using
C<DateTime::TimeZone::Alias>, any aliases you've created will be valid.

=head2 DateTime::TimeZone->all_names

This returns a pre-sorted list of all the time zone names.  This list does not
include link names.  In scalar context, it returns an array reference, while in
list context it returns an array.

=head2 DateTime::TimeZone->categories

This returns a list of all time zone categories.  In scalar context, it returns
an array reference, while in list context it returns an array.

=head2 DateTime::TimeZone->links

This returns a hash of all time zone links, where the keys are the old,
deprecated names, and the values are the new names.  In scalar context, it
returns a hash reference, while in list context it returns a hash.

=head2 DateTime::TimeZone->names_in_category( $category )

Given a valid category, this method returns a list of the names in that
category, without the category portion.  So the list for the "America" category
would include the strings "Chicago", "Kentucky/Monticello", and "New_York". In
scalar context, it returns an array reference, while in list context it returns
an array.

=head2 DateTime::TimeZone->countries()

Returns a sorted list of all the valid country codes (in lower-case) which can
be passed to C<names_in_country()>. In scalar context, it returns an array
reference, while in list context it returns an array.

If you need to convert country codes to names or vice versa you can use
C<Locale::Country> to do so. Note that one of the codes returned is "uk", which
is an alias for the country code "gb", and is not a valid ISO country code.

=head2 DateTime::TimeZone->names_in_country( $country_code )

Given a two-letter ISO3166 country code, this method returns a list of time
zones used in that country. The country code may be of any case. In scalar
context, it returns an array reference, while in list context it returns an
array.

This list is returned in an order vaguely based on geography and population. In
general, the least used zones come last, but there are not guarantees of a
specific order from one release to the next. This order is probably the best
option for presenting zones names to end users.

=head2 DateTime::TimeZone->offset_as_seconds( $offset )

Given an offset as a string, this returns the number of seconds represented by
the offset as a positive or negative number.  Returns C<undef> if $offset is
not in the range C<-99:59:59> to C<+99:59:59>.

The offset is expected to match either
C</^([\+\-])?(\d\d?):(\d\d)(?::(\d\d))?$/> or
C</^([\+\-])?(\d\d)(\d\d)(\d\d)?$/>.  If it doesn't match either of these,
C<undef> will be returned.

This means that if you want to specify hours as a single digit, then each
element of the offset must be separated by a colon (:).

=head2 DateTime::TimeZone->offset_as_string( $offset, $sep )

Given an offset as a number, this returns the offset as a string. Returns
C<undef> if $offset is not in the range C<-359999> to C<359999>.

You can also provide an optional separator which will go between the hours,
minutes, and seconds (if applicable) portions of the offset.

=head2 Storable Hooks

This module provides freeze and thaw hooks for C<Storable> so that the huge
data structures for Olson time zones are not actually stored in the serialized
structure.

If you subclass C<DateTime::TimeZone>, you will inherit its hooks, which may
not work for your module, so please test the interaction of your module with
Storable.

=head1 LOADING TIME ZONES IN A PRE-FORKING SYSTEM

If you are running an application that does pre-forking (for example with
Starman), then you should try to load all the time zones that you'll need in
the parent process. Time zones are loaded on-demand, so loading them once in
each child will waste memory that could otherwise be shared.

=head1 CREDITS

This module was inspired by Jesse Vincent's work on Date::ICal::Timezone, and
written with much help from the datetime@perl.org list.

=head1 SEE ALSO

datetime@perl.org mailing list

The tools directory of the DateTime::TimeZone distribution includes two scripts
that may be of interest to some people.  They are parse_olson and
tests_from_zdump.  Please run them with the --help flag to see what they can be
used for.

=head1 SUPPORT

Support for this module is provided via the datetime@perl.org email list.

Bugs may be submitted at L<https://github.com/houseabsolute/DateTime-TimeZone/issues>.

=head1 SOURCE

The source code repository for DateTime-TimeZone can be found at L<https://github.com/houseabsolute/DateTime-TimeZone>.

=head1 DONATIONS

If you'd like to thank me for the work I've done on this module, please
consider making a "donation" to me via PayPal. I spend a lot of free time
creating free software, and would appreciate any support you'd care to offer.

Please note that B<I am not suggesting that you must do this> in order for me
to continue working on this particular software. I will continue to do so,
inasmuch as I have in the past, for as long as it interests me.

Similarly, a donation made in this way will probably not make me work on this
software much more, unless I get so many donations that I can consider working
on free software full time (let's all have a chuckle at that together).

To donate, log into PayPal and send money to autarch@urth.org, or use the
button at L<https://houseabsolute.com/foss-donations/>.

=head1 AUTHOR

Dave Rolsky <autarch@urth.org>

=head1 CONTRIBUTORS

=for stopwords Alexey Molchanov Alfie John Andrew Paprocki Brian Fraser Bron Gondwana Daisuke Maki David Pinkowitz guillermo.galindo Iain Truskett Jakub Wilk James E Keenan Joshua Hoblitt Karen Etheridge karupanerura kclaggett Matthew Horsfall Mohammad S Anwar Olaf Alders Peter Rabbitson Tom Wyant

=over 4

=item *

Alexey Molchanov <alexey.molchanov@gmail.com>

=item *

Alfie John <alfiej@fastmail.fm>

=item *

Andrew Paprocki <apaprocki@bloomberg.net>

=item *

Brian Fraser <brian.fraser@booking.com>

=item *

Bron Gondwana <brong@fastmail.fm>

=item *

Daisuke Maki <dmaki@cpan.org>

=item *

David Pinkowitz <dave@pinkowitz.com>

=item *

guillermo.galindo <guillermo.galindo@meteologica.com>

=item *

Iain Truskett <deceased>

=item *

Jakub Wilk <jwilk@jwilk.net>

=item *

James E Keenan <jkeenan@cpan.org>

=item *

Joshua Hoblitt <jhoblitt@cpan.org>

=item *

Karen Etheridge <ether@cpan.org>

=item *

karupanerura <karupa@cpan.org>

=item *

kclaggett <kclaggett@proofpoint.com>

=item *

Matthew Horsfall <wolfsage@gmail.com>

=item *

Mohammad S Anwar <mohammad.anwar@yahoo.com>

=item *

Olaf Alders <olaf@wundersolutions.com>

=item *

Peter Rabbitson <ribasushi@cpan.org>

=item *

Tom Wyant <wyant@cpan.org>

=back

=head1 COPYRIGHT AND LICENSE

This software is copyright (c) 2026 by Dave Rolsky.

This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.

The full text of the license can be found in the
F<LICENSE> file included with this distribution.

=cut
