NAME
    DateTime::TimeZone::ICal - iCal VTIMEZONE entry to DateTime::TimeZone

VERSION
    Version 0.04

SYNOPSIS
        use Data::ICal;
        use DateTime::Format::ICal;
        use DateTime::TimeZone::ICal;

        my $ical = Data::ICal->new(filename => 'foo.ics');

        # generate a table of time zones
        my (%tz, @events);
        for my $entry (@{$ical->entries}) {
            my $type = $entry->ical_entry_type;
            if ($type eq 'VTIMEZONE') {
                my $dtz = DateTime::TimeZone::ICal->from_ical_entry($entry);
                $tz{$dtz->name} = $dtz;
            }
            elsif ($type eq 'VEVENT') {
                push @events, $entry;
            }
            # ... handle other iCal objects ...
         }

         # now we can use this dictionary of time zones elsewhere:

         for my $event (@events) {
             # get a property that is a date
             my ($dtstart) = @{$event->property('dtstart')};

             # get the time zone key from the property parameters
             my $tzid = $dtstart->parameters->{TZID};

             # convert the date in the ordinary fashion
             my $dt = DateTime::Format::ICal->parse_datetime($dtstart->value);

             # the datetime will be 'floating', therefore unaffected
             $dt->set_time_zone($tz{$tzid}) if $tzid and $tz{$tzid};

             # ... do other processing ...
         }

DESCRIPTION
    Conforming iCal documents (RFC 5545
    <https://tools.ietf.org/html/rfc5545>) have three ways to represent
    "DATE-TIME" values: UTC, local, and specified through the "TZID"
    mechanism. "TZID" *parameters* in relevant properties are references to
    the same "TZID" *property* in one of a list of "VTIMEZONE" objects,
    where the information about UTC offsets and their recurrence is embedded
    in the document.

    In practice, many generators of iCal documents use, as "TZID" keys,
    valid labels from the Olson database <http://www.iana.org/time-zones>,
    but others, notably Microsoft Outlook, do not. RFC 5545 explicitly
    declines to specify a naming convention, so it is sometimes necessary to
    construct the time zone offsets and daylight savings changes from the
    "VTIMEZONE" data itself, rather than just inferring it from the name.
    That's where this module comes in.

METHODS
    The only differences in interface for this module are its constructor
    and one method, "from_ical_entry". The rest of the interface should work
    exactly the same way as DateTime::TimeZone, so please consult its
    documentation for other functionality.

    This module overrides the following methods:

    *   name

    *   category

    *   is_floating

    *   is_olson

    *   offset_for_datetime

    *   offset_for_local_datetime

    *   is_dst_for_datetime

    *   short_name_for_datetime

    *   is_utc

    *   has_dst_changes

  new %PARAMS
    The constructor has been modified to permit the assembly of a time zone
    specification from piecemeal data. These are the following
    initialization parameters:

    tzid
        This is the "TZID" of the iCal entry. Note that the accessor to
        retrieve the value from an instantiated object is "name", for
        congruence with DateTime::TimeZone.

    standard
        This is an "ARRAY" reference of DateTime::TimeZone::ICal::Spec
        instances, or otherwise of "HASH" references congruent to that
        module's constructor, which will be coerced into said objects. This
        parameter is *required*, and there must be *at least* one member in
        the "ARRAY".

    daylight
        Same deal but for Daylight Savings Time. This parameter is optional,
        as is its contents.

    In practice you may not need to ever use this constructor directly, but
    it may come in handy for instances where you need to compose
    non-standard time zone behaviour from scratch.

  from_ical_entry $ENTRY [, $USE_DATA ]
    This class method converts a Data::ICal::Entry object of type
    "VTIMEZONE" into a DateTime::TimeZone::ICal object. It will "croak" if
    the input is malformed, so wrap it in an "eval" or equivalent if you
    expect that possibility.

    This method attempts to check if an existing DateTime::TimeZone can be
    instantiated from the "TZID", thus skipping over any local processing.
    This behaviour can be overridden with the $USE_DATA flag.

AUTHOR
    Dorian Taylor, "<dorian at cpan.org>"

BUGS
    Please report any bugs or feature requests to
    "bug-datetime-timezone-ical at rt.cpan.org", or through the web
    interface at
    <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=DateTime-TimeZone-ICal>.
    I will be notified, and then you'll automatically be notified of
    progress on your bug as I make changes.

SUPPORT
    You can find documentation for this module with the perldoc command.

        perldoc DateTime::TimeZone::ICal

    You can also look for information at:

    *   RT: CPAN's request tracker (report bugs here)

        <http://rt.cpan.org/NoAuth/Bugs.html?Dist=DateTime-TimeZone-ICal>

    *   AnnoCPAN: Annotated CPAN documentation

        <http://annocpan.org/dist/DateTime-TimeZone-ICal>

    *   CPAN Ratings

        <http://cpanratings.perl.org/d/DateTime-TimeZone-ICal>

    *   Search CPAN

        <http://search.cpan.org/dist/DateTime-TimeZone-ICal/>

SEE ALSO
    DateTime::TimeZone
    DateTime::Format::ICal
    Data::ICal
    RFC 5545 <https://tools.ietf.org/html/rfc5545>
    IANA Time Zones (Olson Database) <http://www.iana.org/time-zones>

LICENSE AND COPYRIGHT
    Copyright 2015 Dorian Taylor.

    Licensed under the Apache License, Version 2.0 (the "License"); you may
    not use this file except in compliance with the License. You may obtain
    a copy of the License at <http://www.apache.org/licenses/LICENSE-2.0>

    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.

