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1 .\" $NetBSD: zic.8,v 1.20 2012/08/09 12:38:26 christos Exp $
2 .Dd December 20, 2003
3 .Dt ZIC 8
4 .Os
5 .Sh NAME
6 .Nm zic
7 .Nd time zone compiler
8 .Sh SYNOPSIS
9 .Nm
10 .Op Fl \-version
11 .Op Fl d Ar directory
12 .Op Fl L Ar leapsecondfilename
13 .Op Fl l Ar localtime
14 .Op Fl p Ar posixrules
15 .Op Fl s
16 .Op Fl v
17 .Op Fl y Ar command
18 .Op Ar Filename ...
19 .Sh DESCRIPTION
20 .Nm
21 reads text from the file(s) named on the command line
22 and creates the time conversion information files specified in this input.
23 If a
24 .Ar filename
25 is
26 .Ar \&- ,
27 the standard input is read.
28 .Pp
29 These options are available:
30 .Bl -tag -width XXXXXXXXXX -compact
31 .It Fl \-version
32 Output version information and exit.
33 .It Fl d Ar directory
34 Create time conversion information files in the named directory rather than
35 in the standard directory named below.
36 .It Fl L Ar leapsecondfilename
37 Read leap second information from the file with the given name.
38 If this option is not used,
39 no leap second information appears in output files.
40 .It Fl l Ar timezone
41 Use the given time zone as local time.
42 .Nm
43 will act as if the input contained a link line of the form
44 .Dl Link timezone localtime
45 .It Fl p Ar timezone
46 Use the given time zone's rules when handling POSIX-format
47 time zone environment variables.
48 .Nm
49 will act as if the input contained a link line of the form
50 .Dl Link timezone posixrules
51 .It Fl s
52 Limit time values stored in output files to values that are the same
53 whether they're taken to be signed or unsigned.
54 You can use this option to generate SVVS-compatible files.
55 .It Fl v
56 Complain if a year that appears in a data file is outside the range
57 of years representable by
58 .Xr time 3
59 values.
60 Also complain if a time of 24:00
61 .Pq which cannot be handled by pre-1998 versions of Nm
62 appears in the input.
63 .It Fl y Ar command
64 Use the given
65 .Ar command
66 rather than
67 .Em yearistype
68 when checking year types (see below).
69 .Pp
70 Input lines are made up of fields.
71 Fields are separated from one another by any number of white space characters.
72 Leading and trailing white space on input lines is ignored.
73 An unquoted sharp character (#) in the input introduces a comment which extends
74 to the end of the line the sharp character appears on.
75 White space characters and sharp characters may be enclosed in double
76 quotes
77 .Pq \&"
78 .\" XXX "
79 if they're to be used as part of a field.
80 Any line that is blank (after comment stripping) is ignored.
81 Non-blank lines are expected to be of one of three types:
82 rule lines, zone lines, and link lines.
83 .Pp
84 Names (such as month names) must be in English and are case insensitive.
85 Abbreviations, if used, must be unambiguous in context.
86 .Pp
87 A rule line has the form
88 .Dl Rule NAME FROM TO TYPE IN ON AT SAVE LETTER/S
89 For example:
90 .Dl Rule US 1967 1973 \- Apr lastSun 2:00 1:00 D
91 The fields that make up a rule line are:
92 .Bl -tag -width "LETTER/S" -compact
93 .It NAME
94 Gives the (arbitrary) name of the set of rules this rule is part of.
95 .It FROM
96 Gives the first year in which the rule applies.
97 Any integer year can be supplied; the Gregorian calendar is assumed.
98 The word
99 .Em minimum
100 (or an abbreviation) means the minimum year representable as an integer.
101 The word
102 .Em maximum
103 (or an abbreviation) means the maximum year representable as an integer.
104 Rules can describe times that are not representable as time values,
105 with the unrepresentable times ignored; this allows rules to be portable
106 among hosts with differing time value types.
107 .It TO
108 Gives the final year in which the rule applies.
109 In addition to
110 .Em minimum
111 and
112 .Em maximum
113 (as above),
114 the word
115 .Em only
116 (or an abbreviation)
117 may be used to repeat the value of the
118 .Em FROM
119 field.
120 .It TYPE
121 Gives the type of year in which the rule applies.
122 If
123 .Em TYPE
124 is
125 .Em \&-
126 then the rule applies in all years between
127 .Em FROM
128 and
129 .Em TO
130 inclusive.
131 If
132 .Em TYPE
133 is something else, then
134 .Nm
135 executes the command
136 .Pp
137 .Ic yearistype Ar year type
138 .Pp
139 to check the type of a year:
140 an exit status of zero is taken to mean that the year is of the given type;
141 an exit status of one is taken to mean that the year is not of the given type.
142 .It IN
143 Names the month in which the rule takes effect.
144 Month names may be abbreviated.
145 .It ON
146 Gives the day on which the rule takes effect.
147 Recognized forms include:
148 .Bl -tag -width lastSun -compact -offset indent
149 .It 5
150 the fifth of the month
151 .It lastSun
152 the last Sunday in the month
153 .It lastMon
154 the last Monday in the month
155 .It Sun\*[Ge]8
156 first Sunday on or after the eighth
157 .It Sun\*[Le]25
158 last Sunday on or before the 25th
159 .El
160 Names of days of the week may be abbreviated or spelled out in full.
161 Note that there must be no spaces within the
162 .Em ON
163 field.
164 .It AT
165 Gives the time of day at which the rule takes effect.
166 Recognized forms include:
167 .Bl -tag -width "1X28X14" -compact -offset indent
168 .It 2
169 time in hours
170 .It 2:00
171 time in hours and minutes
172 .It 15:00
173 24-hour format time (for times after noon)
174 .It 1:28:14
175 time in hours, minutes, and seconds
176 .It \-
177 equivalent to 0
178 .El
179 where hour 0 is midnight at the start of the day,
180 and hour 24 is midnight at the end of the day.
181 Any of these forms may be followed by the letter
182 .Em w
183 if the given time is local
184 .Dq wall clock
185 time,
186 .Em s
187 if the given time is local
188 .Dq standard
189 time, or
190 .Em u
191 (or
192 .Em g
193 or
194 .Em z )
195 if the given time is universal time;
196 in the absence of an indicator,
197 wall clock time is assumed.
198 .It SAVE
199 Gives the amount of time to be added to local standard time when the rule is in
200 effect.
201 This field has the same format as the
202 .Em AT
203 field
204 (although, of course, the
205 .Em w
206 and
207 .Em s
208 suffixes are not used).
209 .It LETTER/S
210 Gives the
211 .Dq variable part
212 (for example, the
213 .Dq S
214 or
215 .Dq D
216 in
217 .Dq EST
218 or
219 .Dq EDT )
220 of time zone abbreviations to be used when this rule is in effect.
221 If this field is
222 .Em \&- ,
223 the variable part is null.
224 .El
225 .Pp
226 A zone line has the form
227 .sp
228 .Dl Zone NAME GMTOFF RULES/SAVE FORMAT [UNTILYEAR [MONTH [DAY [TIME]]]]
229 For example:
230 .Dl Zone Australia/Adelaide 9:30 Aus CST 1971 Oct 31 2:00
231 The fields that make up a zone line are:
232 .Bl -tag -width "RULES/SAVE" -compact
233 .It NAME
234 The name of the time zone.
235 This is the name used in creating the time conversion information file for the
236 zone.
237 .It GMTOFF
238 The amount of time to add to UTC to get standard time in this zone.
239 This field has the same format as the
240 .Em AT
241 and
242 .Em SAVE
243 fields of rule lines;
244 begin the field with a minus sign if time must be subtracted from UTC.
245 .It RULES/SAVE
246 The name of the rule(s) that apply in the time zone or,
247 alternatively, an amount of time to add to local standard time.
248 If this field is
249 .Em \&-
250 then standard time always applies in the time zone.
251 .It FORMAT
252 The format for time zone abbreviations in this time zone.
253 The pair of characters
254 .Em %s
255 is used to show where the
256 .Dq variable part
257 of the time zone abbreviation goes.
258 Alternatively,
259 a slash
260 .Pq \&/
261 separates standard and daylight abbreviations.
262 .It UNTILYEAR [MONTH [DAY [TIME]]]
263 The time at which the UTC offset or the rule(s) change for a location.
264 It is specified as a year, a month, a day, and a time of day.
265 If this is specified,
266 the time zone information is generated from the given UTC offset
267 and rule change until the time specified.
268 The month, day, and time of day have the same format as the IN, ON, and AT
269 fields of a rule; trailing fields can be omitted, and default to the
270 earliest possible value for the missing fields.
271 .El
272 The next line must be a
273 .Dq continuation
274 line; this has the same form as a zone line except that the
275 string
276 .Dq Zone
277 and the name are omitted, as the continuation line will
278 place information starting at the time specified as the
279 .Em until
280 information in the previous line in the file used by the previous line.
281 Continuation lines may contain
282 .Em until
283 information, just as zone lines do, indicating that the next line is a further
284 continuation.
285 .Pp
286 A link line has the form
287 .Dl Link LINK-FROM LINK-TO
288 For example:
289 .Dl Link Europe/Istanbul Asia/Istanbul
290 The
291 .Em LINK-FROM
292 field should appear as the
293 .Em NAME
294 field in some zone line;
295 the
296 .Em LINK-TO
297 field is used as an alternative name for that zone.
298 .Pp
299 Except for continuation lines,
300 lines may appear in any order in the input.
301 .Pp
302 Lines in the file that describes leap seconds have the following form:
303 .Dl Leap YEAR MONTH DAY HH:MM:SS CORR R/S
304 For example:
305 .Dl Leap 1974 Dec 31 23:59:60 + S
306 The
307 .Em YEAR ,
308 .Em MONTH ,
309 .Em DAY ,
310 and
311 .Em HH:MM:SS
312 fields tell when the leap second happened.
313 The
314 .Em CORR
315 field
316 should be
317 .Dq \&+
318 if a second was added
319 or
320 .Dq \&-
321 if a second was skipped.
322 .\" There's no need to document the following, since it's impossible for more
323 .\" than one leap second to be inserted or deleted at a time.
324 .\" The C Standard is in error in suggesting the possibility.
325 .\" See Terry J Quinn, The BIPM and the accurate measure of time,
326 .\" Proc IEEE 79, 7 (July 1991), 894-905.
327 .\" or
328 .\" .Dq ++
329 .\" if two seconds were added
330 .\" or
331 .\" .Dq --
332 .\" if two seconds were skipped.
333 The
334 .Em R/S
335 field
336 should be (an abbreviation of)
337 .Dq Stationary
338 if the leap second time given by the other fields should be interpreted as UTC
339 or
340 (an abbreviation of)
341 .Dq Rolling
342 if the leap second time given by the other fields should be interpreted as
343 local wall clock time.
344 .El
345 .Sh EXTENDED EXAMPLE
346 Here is an extended example of
347 .Ic zic
348 input, intended to illustrate many of its features.
349 .Bl -column -compact "# Rule" "Swiss" "FROM" "1995" "TYPE" "Oct" "lastSun" "1:00u" "SAVE" "LETTER/S"
350 .It # Rule NAME FROM TO TYPE IN ON AT SAVE LETTER/S
351 .It Rule Swiss 1940 only - Nov 2 0:00 1:00 S
352 .It Rule Swiss 1940 only - Dec 31 0:00 0 -
353 .It Rule Swiss 1941 1942 - May Sun>=1 2:00 1:00 S
354 .It Rule Swiss 1941 1942 - Oct Sun>=1 0:00 0
355 .Pp
356 .It Rule EU 1977 1980 - Apr Sun>=1 1:00u 1:00 S
357 .It Rule EU 1977 only - Sep lastSun 1:00u 0 -
358 .It Rule EU 1978 only - Oct 1 1:00u 0 -
359 .It Rule EU 1979 1995 - Sep lastSun 1:00u 0 -
360 .It Rule EU 1981 max - Mar lastSun 1:00u 1:00 S
361 .It Rule EU 1996 max - Oct lastSun 1:00u 0 -
362 .El
363 .Pp
364 .Bl -column -compact "# Zone" "Europe/Zurich" "0:29:44" "RULES" "FORMAT" "UNTIL"
365 .It # Zone NAME GMTOFF RULES FORMAT UNTIL
366 .It Zone Europe/Zurich 0:34:08 - LMT 1848 Sep 12
367 .It 0:29:44 - BMT 1894 Jun
368 .It 1:00 Swiss CE%sT 1981
369 .It 1:00 EU CE%sT
370 .It Link Europe/Zurich Switzerland
371 .El
372 .Pp
373 In this example, the zone is named Europe/Zurich but it has an alias
374 as Switzerland.
375 Zurich was 34 minutes and 8 seconds west of GMT until
376 1848-09-12 at 00:00, when the offset changed to 29 minutes and 44
377 seconds.
378 After 1894-06-01 at 00:00 Swiss daylight saving rules (defined
379 with lines beginning with "Rule Swiss") apply, and the GMT offset
380 became one hour.
381 From 1981 to the present, EU daylight saving rules have
382 applied, and the UTC offset has remained at one hour.
383 .Pp
384 In 1940, daylight saving time applied from November 2 at 00:00 to
385 December 31 at 00:00.
386 In 1941 and 1942, daylight saving time applied
387 from the first Sunday in May at 02:00 to the first Sunday in October
388 at 00:00.
389 The pre-1981 EU daylight-saving rules have no effect
390 here, but are included for completeness.
391 Since 1981, daylight
392 saving has begun on the last Sunday in March at 01:00 UTC.
393 Until 1995 it ended the last Sunday in September at 01:00 UTC,
394 but this changed to the last Sunday in October starting in 1996.
395 .Pp
396 For purposes of
397 display, "LMT" and "BMT" were initially used, respectively.
398 Since
399 Swiss rules and later EU rules were applied, the display name for the
400 timezone has been CET for standard time and CEST for daylight saving
401 time.
402 .Sh NOTES
403 For areas with more than two types of local time,
404 you may need to use local standard time in the
405 .Em AT
406 field of the earliest transition time's rule to ensure that
407 the earliest transition time recorded in the compiled file is correct.
408 .Pp
409 If,
410 for a particular zone,
411 a clock advance caused by the start of daylight saving
412 coincides with and is equal to
413 a clock retreat caused by a change in UTC offset,
414 .Ic zic
415 produces a single transition to daylight saving at the new UTC offset
416 (without any change in wall clock time).
417 To get separate transitions
418 use multiple zone continuation lines
419 specifying transition instants using universal time.
420 .Sh FILES
421 .Pa /usr/share/zoneinfo
422 - standard directory used for created files
423 .Sh SEE ALSO
424 .Xr ctime 3 ,
425 .Xr tzfile 5 ,
426 .Xr zdump 8
427 .\" @(#)zic.8 8.6
428 .\" This file is in the public domain, so clarified as of
429 .\" 2009-05-17 by Arthur David Olson.