DateTime::TimeZone(3pm)

1DateTime::TimeZone(3) User Contributed Perl DocumentationDateTime::TimeZone(3)
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NAME

6       DateTime::TimeZone - Time zone object base class and factory
7

SYNOPSIS

9         use DateTime;
10         use DateTime::TimeZone;
11
12         my $tz = DateTime::TimeZone->new( name => 'America/Chicago' );
13
14         my $dt = DateTime->now();
15         my $offset = $tz->offset_for_datetime($dt);
16

DESCRIPTION

18       This class is the base class for all time zone objects.  A time zone is
19       represented internally as a set of observances, each of which describes
20       the offset from GMT for a given time period.
21
22       Note that without the "DateTime.pm" module, this module does not do
23       much.  It's primary interface is through a "DateTime" object, and most
24       users will not need to directly use "DateTime::TimeZone" methods.
25

USAGE

27       This class has the following methods:
28
29   DateTime::TimeZone->new( name => $tz_name )
30       Given a valid time zone name, this method returns a new time zone
31       blessed into the appropriate subclass.  Subclasses are named for the
32       given time zone, so that the time zone "America/Chicago" is the
33       DateTime::TimeZone::America::Chicago class.
34
35       If the name given is a "link" name in the Olson database, the object
36       created may have a different name.  For example, there is a link from
37       the old "EST5EDT" name to "America/New_York".
38
39       When loading a time zone from the Olson database, the constructor
40       checks the version of the loaded class to make sure it matches the
41       version of the current DateTime::TimeZone installation. If they do not
42       match it will issue a warning. This is useful because time zone names
43       may fall out of use, but you may have an old module file installed for
44       that time zone.
45
46       There are also several special values that can be given as names.
47
48       If the "name" parameter is "floating", then a
49       "DateTime::TimeZone::Floating" object is returned.  A floating time
50       zone does have any offset, and is always the same time.  This is useful
51       for calendaring applications, which may need to specify that a given
52       event happens at the same local time, regardless of where it occurs.
53       See RFC 2445 for more details.
54
55       If the "name" parameter is "UTC", then a "DateTime::TimeZone::UTC"
56       object is returned.
57
58       If the "name" is an offset string, it is converted to a number, and a
59       "DateTime::TimeZone::OffsetOnly" object is returned.
60
61       The "local" time zone
62
63       If the "name" parameter is "local", then the module attempts to
64       determine the local time zone for the system.
65
66       The method for finding the local zone varies by operating system. See
67       the appropriate module for details of how we check for the local time
68       zone.
69
70       ·   DateTime::TimeZone::Local::Unix
71
72       ·   DateTime::TimeZone::Local::Win32
73
74       ·   DateTime::TimeZone::Local::VMS
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76       If a local time zone is not found, then an exception will be thrown.
77
78   $tz->offset_for_datetime( $dt )
79       Given a "DateTime" object, this method returns the offset in seconds
80       for the given datetime.  This takes into account historical time zone
81       information, as well as Daylight Saving Time.  The offset is determined
82       by looking at the object's UTC Rata Die days and seconds.
83
84   $tz->offset_for_local_datetime( $dt )
85       Given a "DateTime" object, this method returns the offset in seconds
86       for the given datetime.  Unlike the previous method, this method uses
87       the local time's Rata Die days and seconds.  This should only be done
88       when the corresponding UTC time is not yet known, because local times
89       can be ambiguous due to Daylight Saving Time rules.
90
91   $tz->name
92       Returns the name of the time zone.  If this value is passed to the
93       "new()" method, it is guaranteed to create the same object.
94
95   $tz->short_name_for_datetime( $dt )
96       Given a "DateTime" object, this method returns the "short name" for the
97       current observance and rule this datetime is in.  These are names like
98       "EST", "GMT", etc.
99
100       It is strongly recommended that you do not rely on these names for
101       anything other than display.  These names are not official, and many of
102       them are simply the invention of the Olson database maintainers.
103       Moreover, these names are not unique.  For example, there is an "EST"
104       at both -0500 and +1000/+1100.
105
106   $tz->is_floating
107       Returns a boolean indicating whether or not this object represents a
108       floating time zone, as defined by RFC 2445.
109
110   $tz->is_utc
111       Indicates whether or not this object represents the UTC (GMT) time
112       zone.
113
114   $tz->has_dst_changes
115       Indicates whether or not this zone has ever had a change to and from
116       DST, either in the past or future.
117
118   $tz->is_olson
119       Returns true if the time zone is a named time zone from the Olson
120       database.
121
122   $tz->category
123       Returns the part of the time zone name before the first slash.  For
124       example, the "America/Chicago" time zone would return "America".
125
126   DateTime::TimeZone->is_valid_name($name)
127       Given a string, this method returns a boolean value indicating whether
128       or not the string is a valid time zone name.  If you are using
129       "DateTime::TimeZone::Alias", any aliases you've created will be valid.
130
131   DateTime::TimeZone->all_names
132       This returns a pre-sorted list of all the time zone names.  This list
133       does not include link names.  In scalar context, it returns an array
134       reference, while in list context it returns an array.
135
136   DateTime::TimeZone->categories
137       This returns a list of all time zone categories.  In scalar context, it
138       returns an array reference, while in list context it returns an array.
139
140   DateTime::TimeZone->links
141       This returns a hash of all time zone links, where the keys are the old,
142       deprecated names, and the values are the new names.  In scalar context,
143       it returns a hash reference, while in list context it returns a hash.
144
145   DateTime::TimeZone->names_in_category( $category )
146       Given a valid category, this method returns a list of the names in that
147       category, without the category portion.  So the list for the "America"
148       category would include the strings "Chicago", "Kentucky/Monticello",
149       and "New_York". In scalar context, it returns an array reference, while
150       in list context it returns an array.
151
152       The list is returned in order of population by zone, which should mean
153       that this order will be the best to use for most UIs.
154
155   DateTime::TimeZone->countries()
156       Returns a sorted list of all the valid country codes (in lower-case)
157       which can be passed to "names_in_country()". In scalar context, it
158       returns an array reference, while in list context it returns an array.
159
160       If you need to convert country codes to names or vice versa you can use
161       "Locale::Country" to do so.
162
163   DateTime::TimeZone->names_in_country( $country_code )
164       Given a two-letter ISO3166 country code, this method returns a list of
165       time zones used in that country. The country code may be of any case.
166       In scalar context, it returns an array reference, while in list context
167       it returns an array.
168
169   DateTime::TimeZone->offset_as_seconds( $offset )
170       Given an offset as a string, this returns the number of seconds
171       represented by the offset as a positive or negative number.  Returns
172       "undef" if $offset is not in the range "-99:59:59" to "+99:59:59".
173
174       The offset is expected to match either
175       "/^([\+\-])?(\d\d?):(\d\d)(?::(\d\d))?$/" or
176       "/^([\+\-])?(\d\d)(\d\d)(\d\d)?$/".  If it doesn't match either of
177       these, "undef" will be returned.
178
179       This means that if you want to specify hours as a single digit, then
180       each element of the offset must be separated by a colon (:).
181
182   DateTime::TimeZone->offset_as_string( $offset )
183       Given an offset as a number, this returns the offset as a string.
184       Returns "undef" if $offset is not in the range "-359999" to 359999.
185
186   Storable Hooks
187       This module provides freeze and thaw hooks for "Storable" so that the
188       huge data structures for Olson time zones are not actually stored in
189       the serialized structure.
190
191       If you subclass "DateTime::TimeZone", you will inherit its hooks, which
192       may not work for your module, so please test the interaction of your
193       module with Storable.
194

SUPPORT

196       Support for this module is provided via the datetime@perl.org email
197       list. See http://datetime.perl.org/?MailingList for details.
198
199       Please submit bugs to the CPAN RT system at
200       http://rt.cpan.org/NoAuth/ReportBug.html?Queue=datetime%3A%3Atimezone
201       or via email at bug-datetime-timezone@rt.cpan.org.
202

DONATIONS

204       If you'd like to thank me for the work I've done on this module, please
205       consider making a "donation" to me via PayPal. I spend a lot of free
206       time creating free software, and would appreciate any support you'd
207       care to offer.
208
209       Please note that I am not suggesting that you must do this in order for
210       me to continue working on this particular software. I will continue to
211       do so, inasmuch as I have in the past, for as long as it interests me.
212
213       Similarly, a donation made in this way will probably not make me work
214       on this software much more, unless I get so many donations that I can
215       consider working on free software full time, which seems unlikely at
216       best.
217
218       To donate, log into PayPal and send money to autarch@urth.org or use
219       the button on this page:
220       <http://www.urth.org/~autarch/fs-donation.html>
221

AUTHOR

223       Dave Rolsky <autarch@urth.org>
224

CREDITS

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

231       Copyright (c) 2003-2008 David Rolsky.  All rights reserved.  This
232       program is free software; you can redistribute it and/or modify it
233       under the same terms as Perl itself.
234
235       The full text of the license can be found in the LICENSE file included
236       with this module.
237