1DateTime::TimeZone::SysUtseemrV(C3o)ntributed Perl DocumDeantteaTtiimoen::TimeZone::SystemV(3)
2
6 DateTime::TimeZone::SystemV - System V and POSIX timezone strings
7
9 use DateTime::TimeZone::SystemV;
10 $tz = DateTime::TimeZone::SystemV->new(
12 name => "US Eastern",
13 recipe => "EST5EDT,M3.2.0,M11.1.0");
14 $tz = DateTime::TimeZone::SystemV->new(
15 "EST5EDT,M3.2.0,M11.1.0");
16 if($tz->is_floating) { ...
18 if($tz->is_utc) { ...
19 if($tz->is_olson) { ...
20 $category = $tz->category;
21 $tz_string = $tz->name;
22 if($tz->has_dst_changes) { ...
24 if($tz->is_dst_for_datetime($dt)) { ...
25 $offset = $tz->offset_for_datetime($dt);
26 $abbrev = $tz->short_name_for_datetime($dt);
27 $offset = $tz->offset_for_local_datetime($dt);
28
30 An instance of this class represents a timezone that was specified by
31 means of a System V timezone recipe or an extended form of the same
32 syntax (such as that specified by POSIX). These can express a plain
33 offset from Universal Time, or a system of two offsets (standard and
34 daylight saving time) switching on a yearly cycle according to certain
35 types of rule.
36 This class implements the DateTime::TimeZone interface, so that its
38 instances can be used with DateTime objects.
39
41 This module supports multiple versions of the timezone recipe syntax
42 derived from System V. Specifically, it supports the version specified
43 by POSIX.1, and the extension of the POSIX format that is used by
44 version 3 of the tzfile(5) file format.
45 A timezone may be specified that has a fixed offset by the syntax
47 "aaaooo", or a timezone with DST by the syntax
48 "aaaoooaaa[ooo],rrr,rrr". "aaa" specifies an abbreviation by which an
49 offset is known, "ooo" specifies the offset, and "rrr" is a rule for
50 when DST starts or ends. For backward compatibility, the rules part
51 may also be omitted from a DST-using timezone, in which case some
52 built-in default rules are used; don't rely on those rules being
53 useful.
54 An abbreviation must be a string of three or more characters from ASCII
56 alphanumerics, "+", and "-". If it contains only ASCII alphabetic
57 characters then the abbreviation specification "aaa" may be simply the
58 abbreviation. Otherwise "aaa" must consist of the abbreviation wrapped
59 in angle brackets ("<...>"). The angle bracket form is always allowed.
60 POSIX allows an implementation to set an upper limit on the length of
61 timezone abbreviations. The limit is known as "TZNAME_MAX", and is
62 required to be no less than 6 (characters/bytes). Abbreviations longer
63 than 6 characters are therefore not portable. This class imposes no
64 such limit.
65 An offset (from Universal Time), "ooo", is given in hours, or hours and
67 minutes, or hours and minutes and seconds, with an optional preceding
68 sign. Hours, minutes, and seconds must be separated by colons. The
69 hours may be one or two digits, and the minutes and seconds must be two
70 digits each. The maximum magnitude permitted is 24:59:59. The sign in
71 the specification is the opposite of the sign of the actual offset. If
72 no sign is given then the default is "+", meaning a timezone that is
73 behind UT (or equal to UT if the offset is zero). If no DST offset is
74 specified, it defaults to one hour ahead of the standard offset.
75 A DST-using timezone has one transition to DST and one transition to
77 standard time in each Gregorian year. The transitions may be in either
78 order within the year. If the transitions are in different orders from
79 year to year then the behaviour is undefined; don't rely on it
80 remaining the same in future versions. Likewise, the behaviour is
81 generally undefined if transitions coincide. However, in the tzfile(5)
82 variant, if the rules specify a transition to DST at 00:00 standard
83 time on 1 January and a transition to standard time at 24:00 standard
84 time on 31 December, which makes the transitions coincide with those of
85 adjacent years, then the timezone is treated as observing DST all year.
86 A transition rule "rrr" takes the form "ddd[/ttt]", where "ddd" is the
88 rule giving the day on which the transition notionally takes place and
89 "ttt" is the time of day at which the transition takes place. (A time
90 of day outside the usual 24-hour range can make the transition actually
91 take place on a different day.) The time may be given in hours, or
92 hours and minutes, or hours and minutes and seconds. Hours, minutes,
93 and seconds must be separated by colons. The minutes and seconds must
94 be two digits each. In the POSIX variant, the hours may be one or two
95 digits, with no preceding sign, and the time stated may range from
96 00:00:00 to 24:59:59 (almost an hour into the following day). In the
97 tzfile(5) variant, the hours may be one to three digits, with optional
98 preceding sign, and the time stated may range from -167:59:59 to
99 +167:59:59 (a span of a little over two weeks). If the time is not
100 stated then it defaults to 02:00:00. The time for the transition to
101 DST is interpreted according to the standard offset, and the time for
102 the transition to standard time is interpreted according to the DST
103 offset. (Thus normally the transition time is interpreted according to
104 the offset that prevailed immediately before the transition.)
105 A day rule "ddd" may take three forms. Firstly, "Jnnn" means the
107 month-day date that is the nnnth day of a non-leap year. Thus "J59"
108 means the February 28 and "J60" means March 1 (even in a leap year).
109 February 29 cannot be specified this way.
110 Secondly, if "ddd" is just a decimal number, it means the (1+ddd)th day
112 of the year. February 29 counts in this case, and it is not possible
113 to specify December 31 of a leap year.
114 Thirdly, "ddd" may have the form "Mm.w.d" means day d of the wth week
116 of the mth month. The day is given as a single digit, with "0" meaning
117 Sunday and "6" meaning Saturday. The first week contains days 1 to 7
118 of the month, the second week contains days 8 to 14, and so on. If "w"
119 is "5" then the last week of the month (containing its last seven days)
120 is used, rather than the fifth week (which is incomplete).
121 Examples:
123 MUT-4
125 Mauritius time, since 1907: 4 hours ahead of UT all year.
126 EST5EDT,M3.2.0,M11.1.0
128 US Eastern timezone with DST, from 2007 onwards. 5 hours behind UT
129 in winter and 4 hours behind in summer. Changes on the second
130 Sunday in March and the first Sunday in November, in each case at
131 02:00 local time.
132 NST3:30NDT,M3.2.0/0:01,M11.1.0/0:01
134 Newfoundland timezone with DST, from 2007 onwards. 3.5 hours
135 behind UT in winter and 2.5 hours behind in summer. Changes on the
136 second Sunday in March and the first Sunday in November, in each
137 case at 00:01 local time.
138 GMT0BST,M3.5.0/1,M10.5.0
140 UK civil time, from 1996 onwards. On UT during the winter, calling
141 it "GMT", and 1 hour ahead of UT during the summer, called "BST".
142 Changes on the last Sunday in March and the last Sunday in October,
143 in each case at 01:00 UT.
144 EST-10EST,M10.5.0,M3.5.0/3
146 Australian Eastern timezone, from 2007 onwards. 10 hours ahead of
147 UT in the southern winter (the middle of the calendar year), and 11
148 hours ahead in the southern summer. Changes to DST on the last
149 Sunday in October, and back on the last Sunday in March, in each
150 case at 02:00 standard time (16:00 UT of the preceding day).
151 EET-2EEST,M3.5.4/24,M9.3.6/145
153 Palestinian civil time, from 2012 onwards. 2 hours ahead of UT in
154 winter and 3 hours ahead in summer. Changes at the end (24:00
155 local time) of the last Thursday in March and 01:00 local time on
156 the Friday following the third Saturday in September (that is, the
157 Friday falling between September 21 and September 27 inclusive).
158 The extended time-of-day "145", meaning 01:00 of the day six days
159 after the nominal day, is only valid in the tzfile(5) variant of
160 the System V syntax. The time-of-day "24" is not so restricted,
161 being permitted by POSIX.
162
164 DateTime::TimeZone::SystemV->new(ATTR => VALUE, ...)
165 Constructs and returns a DateTime-compatible timezone object that
166 implements the timezone described by the recipe given in the
167 arguments. The following attributes may be given:
168 name
170 Name for the timezone object. This will be returned by the
171 "name" method described below, and will be included in certain
172 error messages. If not given, then the recipe is used as the
173 timezone name.
174 recipe
176 The short textual timezone recipe, as described in "SYSTEM V
177 TIMEZONE RECIPE SYSTEM". Must be given.
178 system
180 Keyword identifying the particular variant of the recipe system
181 according to which the recipe is to be interpreted. It may be:
182 posix (default)
184 As specified by POSIX.1.
185 tzfile3
187 As specified by version 3 of the tzfile(5) file format.
188 DateTime::TimeZone::SystemV->new(RECIPE)
190 Simpler way to invoke the above constructor in the usual case.
191 Only the recipe is given; it will be interpreted according to POSIX
192 system, and the recipe will also be used as the timezone name.
193
195 These methods are all part of the DateTime::TimeZone interface. See
196 that class for the general meaning of these methods; the documentation
197 below only comments on the specific behaviour of this class.
198 Identification
200 $tz->is_floating
201 Returns false.
202 $tz->is_utc
204 Returns false.
205 $tz->is_olson
207 Returns false.
208 $tz->category
210 Returns "undef", because the category concept doesn't properly
211 apply to these timezones.
212 $tz->name
214 Returns the timezone name. Usually this is the recipe that was
215 supplied to the constructor, but it can be overridden by the
216 constructor's name attribute.
217 Offsets
219 $tz->has_dst_changes
220 Returns a truth value indicating whether the timezone includes a
221 DST offset.
222 $tz->is_dst_for_datetime(DT)
224 DT must be a DateTime-compatible object (specifically, it must
225 implement the "utc_rd_values" method). Returns a truth value
226 indicating whether the timezone is on DST at the instant
227 represented by DT.
228 $tz->offset_for_datetime(DT)
230 DT must be a DateTime-compatible object (specifically, it must
231 implement the "utc_rd_values" method). Returns the offset from UT
232 that is in effect at the instant represented by DT, in seconds.
233 $tz->short_name_for_datetime(DT)
235 DT must be a DateTime-compatible object (specifically, it must
236 implement the "utc_rd_values" method). Returns the time scale
237 abbreviation for the offset that is in effect at the instant
238 represented by DT.
239 $tz->offset_for_local_datetime(DT)
241 DT must be a DateTime-compatible object (specifically, it must
242 implement the "local_rd_values" method). Takes the local time
243 represented by DT (regardless of what absolute time it also
244 represents), and interprets that as a local time in the timezone of
245 the timezone object (not the timezone used in DT). Returns the
246 offset from UT that is in effect at that local time, in seconds.
247 If the local time given is ambiguous due to a nearby offset change,
249 the numerically lower offset (usually the standard one) is returned
250 with no warning of the situation. If the local time given does not
251 exist due to a nearby offset change, the method "die"s saying so.
252
254 DateTime, DateTime::TimeZone, POSIX.1
255 <http://www.opengroup.org/onlinepubs/000095399/basedefs/xbd_chap08.html>,
256 tzfile(5)
257
259 Andrew Main (Zefram) <zefram@fysh.org>
260
262 Copyright (C) 2007, 2009, 2010, 2011, 2012, 2013, 2017 Andrew Main
263 (Zefram) <zefram@fysh.org>
264
266 This module is free software; you can redistribute it and/or modify it
267 under the same terms as Perl itself.
268perl v5.32.0 2020-07-28 DateTime::TimeZone::SystemV(3)