1NAME 2 DateTime::TimeZone - Time zone object base class and factory 3 4SYNOPSIS 5 use DateTime; 6 use DateTime::TimeZone; 7 8 my $tz = DateTime::TimeZone->new( name => 'America/Chicago' ); 9 10 my $dt = DateTime->now(); 11 my $offset = $tz->offset_for_datetime($dt); 12 13DESCRIPTION 14 This class is the base class for all time zone objects. A time zone is 15 represented internally as a set of observances, each of which describes 16 the offset from GMT for a given time period. 17 18 Note that without the `DateTime.pm' module, this module does not do 19 much. It's primary interface is through a `DateTime' object, and most 20 users will not need to directly use `DateTime::TimeZone' methods. 21 22USAGE 23 This class has the following methods: 24 25 DateTime::TimeZone->new( name => $tz_name ) 26 Given a valid time zone name, this method returns a new time zone 27 blessed into the appropriate subclass. Subclasses are named for the 28 given time zone, so that the time zone "America/Chicago" is the 29 DateTime::TimeZone::America::Chicago class. 30 31 If the name given is a "link" name in the Olson database, the object 32 created may have a different name. For example, there is a link from the 33 old "EST5EDT" name to "America/New_York". 34 35 When loading a time zone from the Olson database, the constructor checks 36 the version of the loaded class to make sure it matches the version of 37 the current DateTime::TimeZone installation. If they do not match it 38 will issue a warning. This is useful because time zone names may fall 39 out of use, but you may have an old module file installed for that time 40 zone. 41 42 There are also several special values that can be given as names. 43 44 If the "name" parameter is "floating", then a 45 `DateTime::TimeZone::Floating' object is returned. A floating time zone 46 does have *any* offset, and is always the same time. This is useful for 47 calendaring applications, which may need to specify that a given event 48 happens at the same *local* time, regardless of where it occurs. See RFC 49 2445 for more details. 50 51 If the "name" parameter is "UTC", then a `DateTime::TimeZone::UTC' 52 object is returned. 53 54 If the "name" is an offset string, it is converted to a number, and a 55 `DateTime::TimeZone::OffsetOnly' object is returned. 56 57 The "local" time zone 58 If the "name" parameter is "local", then the module attempts to 59 determine the local time zone for the system. 60 61 The method for finding the local zone varies by operating system. See 62 the appropriate module for details of how we check for the local time 63 zone. 64 65 * DateTime::TimeZone::Local::Unix 66 * DateTime::TimeZone::Local::Win32 67 * DateTime::TimeZone::Local::VMS 68 69 If a local time zone is not found, then an exception will be thrown. 70 71 $tz->offset_for_datetime( $dt ) 72 Given a `DateTime' object, this method returns the offset in seconds for 73 the given datetime. This takes into account historical time zone 74 information, as well as Daylight Saving Time. The offset is determined 75 by looking at the object's UTC Rata Die days and seconds. 76 77 $tz->offset_for_local_datetime( $dt ) 78 Given a `DateTime' object, this method returns the offset in seconds for 79 the given datetime. Unlike the previous method, this method uses the 80 local time's Rata Die days and seconds. This should only be done when 81 the corresponding UTC time is not yet known, because local times can be 82 ambiguous due to Daylight Saving Time rules. 83 84 $tz->name 85 Returns the name of the time zone. If this value is passed to the 86 `new()' method, it is guaranteed to create the same object. 87 88 $tz->short_name_for_datetime( $dt ) 89 Given a `DateTime' object, this method returns the "short name" for the 90 current observance and rule this datetime is in. These are names like 91 "EST", "GMT", etc. 92 93 It is strongly recommended that you do not rely on these names for 94 anything other than display. These names are not official, and many of 95 them are simply the invention of the Olson database maintainers. 96 Moreover, these names are not unique. For example, there is an "EST" at 97 both -0500 and +1000/+1100. 98 99 $tz->is_floating 100 Returns a boolean indicating whether or not this object represents a 101 floating time zone, as defined by RFC 2445. 102 103 $tz->is_utc 104 Indicates whether or not this object represents the UTC (GMT) time zone. 105 106 $tz->has_dst_changes 107 Indicates whether or not this zone has *ever* had a change to and from 108 DST, either in the past or future. 109 110 $tz->is_olson 111 Returns true if the time zone is a named time zone from the Olson 112 database. 113 114 $tz->category 115 Returns the part of the time zone name before the first slash. For 116 example, the "America/Chicago" time zone would return "America". 117 118 DateTime::TimeZone->is_valid_name($name) 119 Given a string, this method returns a boolean value indicating whether 120 or not the string is a valid time zone name. If you are using 121 `DateTime::TimeZone::Alias', any aliases you've created will be valid. 122 123 DateTime::TimeZone->all_names 124 This returns a pre-sorted list of all the time zone names. This list 125 does not include link names. In scalar context, it returns an array 126 reference, while in list context it returns an array. 127 128 DateTime::TimeZone->categories 129 This returns a list of all time zone categories. In scalar context, it 130 returns an array reference, while in list context it returns an array. 131 132 DateTime::TimeZone->links 133 This returns a hash of all time zone links, where the keys are the old, 134 deprecated names, and the values are the new names. In scalar context, 135 it returns a hash reference, while in list context it returns a hash. 136 137 DateTime::TimeZone->names_in_category( $category ) 138 Given a valid category, this method returns a list of the names in that 139 category, without the category portion. So the list for the "America" 140 category would include the strings "Chicago", "Kentucky/Monticello", and 141 "New_York". In scalar context, it returns an array reference, while in 142 list context it returns an array. 143 144 The list is returned in order of population by zone, which should mean 145 that this order will be the best to use for most UIs. 146 147 DateTime::TimeZone->countries() 148 Returns a sorted list of all the valid country codes (in lower-case) 149 which can be passed to `names_in_country()'. In scalar context, it 150 returns an array reference, while in list context it returns an array. 151 152 If you need to convert country codes to names or vice versa you can use 153 `Locale::Country' to do so. 154 155 DateTime::TimeZone->names_in_country( $country_code ) 156 Given a two-letter ISO3166 country code, this method returns a list of 157 time zones used in that country. The country code may be of any case. In 158 scalar context, it returns an array reference, while in list context it 159 returns an array. 160 161 DateTime::TimeZone->offset_as_seconds( $offset ) 162 Given an offset as a string, this returns the number of seconds 163 represented by the offset as a positive or negative number. Returns 164 `undef' if $offset is not in the range `-99:59:59' to `+99:59:59'. 165 166 The offset is expected to match either 167 `/^([\+\-])?(\d\d?):(\d\d)(?::(\d\d))?$/' or 168 `/^([\+\-])?(\d\d)(\d\d)(\d\d)?$/'. If it doesn't match either of these, 169 `undef' will be returned. 170 171 This means that if you want to specify hours as a single digit, then 172 each element of the offset must be separated by a colon (:). 173 174 DateTime::TimeZone->offset_as_string( $offset ) 175 Given an offset as a number, this returns the offset as a string. 176 Returns `undef' if $offset is not in the range `-359999' to `359999'. 177 178 Storable Hooks 179 This module provides freeze and thaw hooks for `Storable' so that the 180 huge data structures for Olson time zones are not actually stored in the 181 serialized structure. 182 183 If you subclass `DateTime::TimeZone', you will inherit its hooks, which 184 may not work for your module, so please test the interaction of your 185 module with Storable. 186 187SUPPORT 188 Support for this module is provided via the datetime@perl.org email 189 list. See http://datetime.perl.org/?MailingList for details. 190 191 Please submit bugs to the CPAN RT system at 192 http://rt.cpan.org/NoAuth/ReportBug.html?Queue=datetime%3A%3Atimezone or 193 via email at bug-datetime-timezone@rt.cpan.org. 194 195DONATIONS 196 If you'd like to thank me for the work I've done on this module, please 197 consider making a "donation" to me via PayPal. I spend a lot of free 198 time creating free software, and would appreciate any support you'd care 199 to offer. 200 201 Please note that I am not suggesting that you must do this in order for 202 me to continue working on this particular software. I will continue to 203 do so, inasmuch as I have in the past, for as long as it interests me. 204 205 Similarly, a donation made in this way will probably not make me work on 206 this software much more, unless I get so many donations that I can 207 consider working on free software full time, which seems unlikely at 208 best. 209 210 To donate, log into PayPal and send money to autarch@urth.org or use the 211 button on this page: http://www.urth.org/~autarch/fs-donation.html 212 213AUTHOR 214 Dave Rolsky <autarch@urth.org> 215 216CREDITS 217 This module was inspired by Jesse Vincent's work on 218 Date::ICal::Timezone, and written with much help from the 219 datetime@perl.org list. 220 221COPYRIGHT 222 Copyright (c) 2003-2008 David Rolsky. All rights reserved. This program 223 is free software; you can redistribute it and/or modify it under the 224 same terms as Perl itself. 225 226 The full text of the license can be found in the LICENSE file included 227 with this module. 228 229SEE ALSO 230 datetime@perl.org mailing list 231 232 http://datetime.perl.org/ 233 234 The tools directory of the DateTime::TimeZone distribution includes two 235 scripts that may be of interest to some people. They are parse_olson and 236 tests_from_zdump. Please run them with the --help flag to see what they 237 can be used for. 238 239