1DateTime::TimeZone(3) User Contributed Perl DocumentationDateTime::TimeZone(3)
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6 DateTime::TimeZone - Time zone object base class and factory
7
9 version 1.42
10
12 use DateTime;
13 use DateTime::TimeZone;
14 my $tz = DateTime::TimeZone->new( name => 'America/Chicago' );
16 my $dt = DateTime->now();
18 my $offset = $tz->offset_for_datetime($dt);
19
21 This class is the base class for all time zone objects. A time zone is
22 represented internally as a set of observances, each of which describes
23 the offset from GMT for a given time period.
24 Note that without the "DateTime.pm" module, this module does not do
26 much. It's primary interface is through a "DateTime" object, and most
27 users will not need to directly use "DateTime::TimeZone" methods.
28
30 This class has the following methods:
31 DateTime::TimeZone->new( name => $tz_name )
33 Given a valid time zone name, this method returns a new time zone
34 blessed into the appropriate subclass. Subclasses are named for the
35 given time zone, so that the time zone "America/Chicago" is the
36 DateTime::TimeZone::America::Chicago class.
37 If the name given is a "link" name in the Olson database, the object
39 created may have a different name. For example, there is a link from
40 the old "EST5EDT" name to "America/New_York".
41 When loading a time zone from the Olson database, the constructor
43 checks the version of the loaded class to make sure it matches the
44 version of the current DateTime::TimeZone installation. If they do not
45 match it will issue a warning. This is useful because time zone names
46 may fall out of use, but you may have an old module file installed for
47 that time zone.
48 There are also several special values that can be given as names.
50 If the "name" parameter is "floating", then a
52 "DateTime::TimeZone::Floating" object is returned. A floating time
53 zone does have any offset, and is always the same time. This is useful
54 for calendaring applications, which may need to specify that a given
55 event happens at the same local time, regardless of where it occurs.
56 See RFC 2445 for more details.
57 If the "name" parameter is "UTC", then a "DateTime::TimeZone::UTC"
59 object is returned.
60 If the "name" is an offset string, it is converted to a number, and a
62 "DateTime::TimeZone::OffsetOnly" object is returned.
63 The "local" time zone
65 If the "name" parameter is "local", then the module attempts to
67 determine the local time zone for the system.
68 The method for finding the local zone varies by operating system. See
70 the appropriate module for details of how we check for the local time
71 zone.
72 · DateTime::TimeZone::Local::Unix
74 · DateTime::TimeZone::Local::Win32
76 · DateTime::TimeZone::Local::VMS
78 If a local time zone is not found, then an exception will be thrown.
80 $tz->offset_for_datetime( $dt )
82 Given a "DateTime" object, this method returns the offset in seconds
83 for the given datetime. This takes into account historical time zone
84 information, as well as Daylight Saving Time. The offset is determined
85 by looking at the object's UTC Rata Die days and seconds.
86 $tz->offset_for_local_datetime( $dt )
88 Given a "DateTime" object, this method returns the offset in seconds
89 for the given datetime. Unlike the previous method, this method uses
90 the local time's Rata Die days and seconds. This should only be done
91 when the corresponding UTC time is not yet known, because local times
92 can be ambiguous due to Daylight Saving Time rules.
93 $tz->is_dst_for_datetime( $dt )
95 Given a "DateTime" object, this method returns true if the DateTime is
96 currently in Daylight Saving Time.
97 $tz->name
99 Returns the name of the time zone.
100 $tz->short_name_for_datetime( $dt )
102 Given a "DateTime" object, this method returns the "short name" for the
103 current observance and rule this datetime is in. These are names like
104 "EST", "GMT", etc.
105 It is strongly recommended that you do not rely on these names for
107 anything other than display. These names are not official, and many of
108 them are simply the invention of the Olson database maintainers.
109 Moreover, these names are not unique. For example, there is an "EST"
110 at both -0500 and +1000/+1100.
111 $tz->is_floating
113 Returns a boolean indicating whether or not this object represents a
114 floating time zone, as defined by RFC 2445.
115 $tz->is_utc
117 Indicates whether or not this object represents the UTC (GMT) time
118 zone.
119 $tz->has_dst_changes
121 Indicates whether or not this zone has ever had a change to and from
122 DST, either in the past or future.
123 $tz->is_olson
125 Returns true if the time zone is a named time zone from the Olson
126 database.
127 $tz->category
129 Returns the part of the time zone name before the first slash. For
130 example, the "America/Chicago" time zone would return "America".
131 DateTime::TimeZone->is_valid_name($name)
133 Given a string, this method returns a boolean value indicating whether
134 or not the string is a valid time zone name. If you are using
135 "DateTime::TimeZone::Alias", any aliases you've created will be valid.
136 DateTime::TimeZone->all_names
138 This returns a pre-sorted list of all the time zone names. This list
139 does not include link names. In scalar context, it returns an array
140 reference, while in list context it returns an array.
141 DateTime::TimeZone->categories
143 This returns a list of all time zone categories. In scalar context, it
144 returns an array reference, while in list context it returns an array.
145 DateTime::TimeZone->links
147 This returns a hash of all time zone links, where the keys are the old,
148 deprecated names, and the values are the new names. In scalar context,
149 it returns a hash reference, while in list context it returns a hash.
150 DateTime::TimeZone->names_in_category( $category )
152 Given a valid category, this method returns a list of the names in that
153 category, without the category portion. So the list for the "America"
154 category would include the strings "Chicago", "Kentucky/Monticello",
155 and "New_York". In scalar context, it returns an array reference, while
156 in list context it returns an array.
157 The list is returned in order of population by zone, which should mean
159 that this order will be the best to use for most UIs.
160 DateTime::TimeZone->countries()
162 Returns a sorted list of all the valid country codes (in lower-case)
163 which can be passed to "names_in_country()". In scalar context, it
164 returns an array reference, while in list context it returns an array.
165 If you need to convert country codes to names or vice versa you can use
167 "Locale::Country" to do so.
168 DateTime::TimeZone->names_in_country( $country_code )
170 Given a two-letter ISO3166 country code, this method returns a list of
171 time zones used in that country. The country code may be of any case.
172 In scalar context, it returns an array reference, while in list context
173 it returns an array.
174 DateTime::TimeZone->offset_as_seconds( $offset )
176 Given an offset as a string, this returns the number of seconds
177 represented by the offset as a positive or negative number. Returns
178 "undef" if $offset is not in the range "-99:59:59" to "+99:59:59".
179 The offset is expected to match either
181 "/^([\+\-])?(\d\d?):(\d\d)(?::(\d\d))?$/" or
182 "/^([\+\-])?(\d\d)(\d\d)(\d\d)?$/". If it doesn't match either of
183 these, "undef" will be returned.
184 This means that if you want to specify hours as a single digit, then
186 each element of the offset must be separated by a colon (:).
187 DateTime::TimeZone->offset_as_string( $offset )
189 Given an offset as a number, this returns the offset as a string.
190 Returns "undef" if $offset is not in the range "-359999" to 359999.
191 Storable Hooks
193 This module provides freeze and thaw hooks for "Storable" so that the
194 huge data structures for Olson time zones are not actually stored in
195 the serialized structure.
196 If you subclass "DateTime::TimeZone", you will inherit its hooks, which
198 may not work for your module, so please test the interaction of your
199 module with Storable.
200
202 Support for this module is provided via the datetime@perl.org email
203 list. See http://datetime.perl.org/wiki/datetime/page/Mailing_List for
204 details.
205 Please submit bugs to the CPAN RT system at
207 http://rt.cpan.org/NoAuth/ReportBug.html?Queue=datetime%3A%3Atimezone
208 or via email at bug-datetime-timezone@rt.cpan.org.
209
211 If you'd like to thank me for the work I've done on this module, please
212 consider making a "donation" to me via PayPal. I spend a lot of free
213 time creating free software, and would appreciate any support you'd
214 care to offer.
215 Please note that I am not suggesting that you must do this in order for
217 me to continue working on this particular software. I will continue to
218 do so, inasmuch as I have in the past, for as long as it interests me.
219 Similarly, a donation made in this way will probably not make me work
221 on this software much more, unless I get so many donations that I can
222 consider working on free software full time, which seems unlikely at
223 best.
224 To donate, log into PayPal and send money to autarch@urth.org or use
226 the button on this page: http://www.urth.org/~autarch/fs-donation.html
227 <http://www.urth.org/~autarch/fs-donation.html>
228
230 This module was inspired by Jesse Vincent's work on
231 Date::ICal::Timezone, and written with much help from the
232 datetime@perl.org list.
233
235 datetime@perl.org mailing list
236 http://datetime.perl.org/
238 The tools directory of the DateTime::TimeZone distribution includes two
240 scripts that may be of interest to some people. They are parse_olson
241 and tests_from_zdump. Please run them with the --help flag to see what
242 they can be used for.
243
245 Dave Rolsky <autarch@urth.org>
246
248 This software is copyright (c) 2011 by Dave Rolsky.
249 This is free software; you can redistribute it and/or modify it under
251 the same terms as the Perl 5 programming language system itself.
252perl v5.12.4 2011-11-07 DateTime::TimeZone(3)