Theory revision 1.10 1 1.10 christos # $NetBSD: Theory,v 1.10 2011/09/04 10:10:26 christos Exp $
2 1.10 christos @(#)Theory 8.6
3 1.9 mlelstv This file is in the public domain, so clarified as of
4 1.9 mlelstv 2009-05-17 by Arthur David Olson.
5 1.2 perry
6 1.2 perry ----- Outline -----
7 1.2 perry
8 1.2 perry Time and date functions
9 1.10 christos Scope of the tz database
10 1.10 christos Names of time zone rule files
11 1.2 perry Time zone abbreviations
12 1.4 kleink Calendrical issues
13 1.8 kleink Time and time zones on Mars
14 1.2 perry
15 1.2 perry ----- Time and date functions -----
16 1.2 perry
17 1.9 mlelstv These time and date functions are upwards compatible with POSIX,
18 1.7 kleink an international standard for UNIX-like systems.
19 1.9 mlelstv As of this writing, the current edition of POSIX is:
20 1.2 perry
21 1.9 mlelstv Standard for Information technology
22 1.9 mlelstv -- Portable Operating System Interface (POSIX (R))
23 1.9 mlelstv -- System Interfaces
24 1.9 mlelstv IEEE Std 1003.1, 2004 Edition
25 1.9 mlelstv <http://www.opengroup.org/online-pubs?DOC=7999959899>
26 1.9 mlelstv <http://www.opengroup.org/pubs/catalog/t041.htm>
27 1.2 perry
28 1.9 mlelstv POSIX has the following properties and limitations.
29 1.2 perry
30 1.9 mlelstv * In POSIX, time display in a process is controlled by the
31 1.9 mlelstv environment variable TZ. Unfortunately, the POSIX TZ string takes
32 1.2 perry a form that is hard to describe and is error-prone in practice.
33 1.9 mlelstv Also, POSIX TZ strings can't deal with other (for example, Israeli)
34 1.2 perry daylight saving time rules, or situations where more than two
35 1.1 jtc time zone abbreviations are used in an area.
36 1.1 jtc
37 1.9 mlelstv The POSIX TZ string takes the following form:
38 1.2 perry
39 1.2 perry stdoffset[dst[offset],date[/time],date[/time]]
40 1.2 perry
41 1.2 perry where:
42 1.6 kleink
43 1.2 perry std and dst
44 1.2 perry are 3 or more characters specifying the standard
45 1.2 perry and daylight saving time (DST) zone names.
46 1.9 mlelstv Starting with POSIX.1-2001, std and dst may also be
47 1.9 mlelstv in a quoted form like "<UTC+10>"; this allows
48 1.9 mlelstv "+" and "-" in the names.
49 1.2 perry offset
50 1.2 perry is of the form `[-]hh:[mm[:ss]]' and specifies the
51 1.2 perry offset west of UTC. The default DST offset is one hour
52 1.2 perry ahead of standard time.
53 1.2 perry date[/time],date[/time]
54 1.2 perry specifies the beginning and end of DST. If this is absent,
55 1.2 perry the system supplies its own rules for DST, and these can
56 1.2 perry differ from year to year; typically US DST rules are used.
57 1.2 perry time
58 1.2 perry takes the form `hh:[mm[:ss]]' and defaults to 02:00.
59 1.2 perry date
60 1.2 perry takes one of the following forms:
61 1.2 perry Jn (1<=n<=365)
62 1.2 perry origin-1 day number not counting February 29
63 1.2 perry n (0<=n<=365)
64 1.2 perry origin-0 day number counting February 29 if present
65 1.2 perry Mm.n.d (0[Sunday]<=d<=6[Saturday], 1<=n<=5, 1<=m<=12)
66 1.2 perry for the dth day of week n of month m of the year,
67 1.2 perry where week 1 is the first week in which day d appears,
68 1.2 perry and `5' stands for the last week in which day d appears
69 1.2 perry (which may be either the 4th or 5th week).
70 1.2 perry
71 1.9 mlelstv Here is an example POSIX TZ string, for US Pacific time using rules
72 1.9 mlelstv appropriate from 1987 through 2006:
73 1.9 mlelstv
74 1.9 mlelstv TZ='PST8PDT,M4.1.0/02:00,M10.5.0/02:00'
75 1.9 mlelstv
76 1.9 mlelstv This POSIX TZ string is hard to remember, and mishandles time stamps
77 1.9 mlelstv before 1987 and after 2006. With this package you can use this
78 1.9 mlelstv instead:
79 1.9 mlelstv
80 1.9 mlelstv TZ='America/Los_Angeles'
81 1.9 mlelstv
82 1.9 mlelstv * POSIX does not define the exact meaning of TZ values like "EST5EDT".
83 1.9 mlelstv Typically the current US DST rules are used to interpret such values,
84 1.2 perry but this means that the US DST rules are compiled into each program
85 1.2 perry that does time conversion. This means that when US time conversion
86 1.1 jtc rules change (as in the United States in 1987), all programs that
87 1.1 jtc do time conversion must be recompiled to ensure proper results.
88 1.1 jtc
89 1.9 mlelstv * In POSIX, there's no tamper-proof way for a process to learn the
90 1.1 jtc system's best idea of local wall clock. (This is important for
91 1.1 jtc applications that an administrator wants used only at certain times--
92 1.1 jtc without regard to whether the user has fiddled the "TZ" environment
93 1.3 jtc variable. While an administrator can "do everything in UTC" to get
94 1.1 jtc around the problem, doing so is inconvenient and precludes handling
95 1.2 perry daylight saving time shifts--as might be required to limit phone
96 1.1 jtc calls to off-peak hours.)
97 1.1 jtc
98 1.9 mlelstv * POSIX requires that systems ignore leap seconds.
99 1.1 jtc
100 1.9 mlelstv These are the extensions that have been made to the POSIX functions:
101 1.1 jtc
102 1.1 jtc * The "TZ" environment variable is used in generating the name of a file
103 1.1 jtc from which time zone information is read (or is interpreted a la
104 1.1 jtc POSIX); "TZ" is no longer constrained to be a three-letter time zone
105 1.1 jtc name followed by a number of hours and an optional three-letter
106 1.1 jtc daylight time zone name. The daylight saving time rules to be used
107 1.1 jtc for a particular time zone are encoded in the time zone file;
108 1.1 jtc the format of the file allows U.S., Australian, and other rules to be
109 1.1 jtc encoded, and allows for situations where more than two time zone
110 1.1 jtc abbreviations are used.
111 1.1 jtc
112 1.1 jtc It was recognized that allowing the "TZ" environment variable to
113 1.2 perry take on values such as "America/New_York" might cause "old" programs
114 1.1 jtc (that expect "TZ" to have a certain form) to operate incorrectly;
115 1.1 jtc consideration was given to using some other environment variable
116 1.1 jtc (for example, "TIMEZONE") to hold the string used to generate the
117 1.1 jtc time zone information file name. In the end, however, it was decided
118 1.1 jtc to continue using "TZ": it is widely used for time zone purposes;
119 1.1 jtc separately maintaining both "TZ" and "TIMEZONE" seemed a nuisance;
120 1.1 jtc and systems where "new" forms of "TZ" might cause problems can simply
121 1.1 jtc use TZ values such as "EST5EDT" which can be used both by
122 1.1 jtc "new" programs (a la POSIX) and "old" programs (as zone names and
123 1.1 jtc offsets).
124 1.1 jtc
125 1.1 jtc * To handle places where more than two time zone abbreviations are used,
126 1.1 jtc the functions "localtime" and "gmtime" set tzname[tmp->tm_isdst]
127 1.1 jtc (where "tmp" is the value the function returns) to the time zone
128 1.9 mlelstv abbreviation to be used. This differs from POSIX, where the elements
129 1.1 jtc of tzname are only changed as a result of calls to tzset.
130 1.1 jtc
131 1.1 jtc * Since the "TZ" environment variable can now be used to control time
132 1.1 jtc conversion, the "daylight" and "timezone" variables are no longer
133 1.2 perry needed. (These variables are defined and set by "tzset"; however, their
134 1.1 jtc values will not be used by "localtime.")
135 1.1 jtc
136 1.1 jtc * The "localtime" function has been set up to deliver correct results
137 1.1 jtc for near-minimum or near-maximum time_t values. (A comment in the
138 1.1 jtc source code tells how to get compatibly wrong results).
139 1.1 jtc
140 1.1 jtc * A function "tzsetwall" has been added to arrange for the system's
141 1.1 jtc best approximation to local wall clock time to be delivered by
142 1.1 jtc subsequent calls to "localtime." Source code for portable
143 1.1 jtc applications that "must" run on local wall clock time should call
144 1.2 perry "tzsetwall();" if such code is moved to "old" systems that don't
145 1.2 perry provide tzsetwall, you won't be able to generate an executable program.
146 1.1 jtc (These time zone functions also arrange for local wall clock time to be
147 1.1 jtc used if tzset is called--directly or indirectly--and there's no "TZ"
148 1.1 jtc environment variable; portable applications should not, however, rely
149 1.1 jtc on this behavior since it's not the way SVR2 systems behave.)
150 1.1 jtc
151 1.9 mlelstv * These functions can account for leap seconds, thanks to Bradley White.
152 1.1 jtc
153 1.2 perry Points of interest to folks with other systems:
154 1.2 perry
155 1.2 perry * This package is already part of many POSIX-compliant hosts,
156 1.2 perry including BSD, HP, Linux, Network Appliance, SCO, SGI, and Sun.
157 1.2 perry On such hosts, the primary use of this package
158 1.2 perry is to update obsolete time zone rule tables.
159 1.2 perry To do this, you may need to compile the time zone compiler
160 1.2 perry `zic' supplied with this package instead of using the system `zic',
161 1.2 perry since the format of zic's input changed slightly in late 1994,
162 1.2 perry and many vendors still do not support the new input format.
163 1.2 perry
164 1.7 kleink * The UNIX Version 7 "timezone" function is not present in this package;
165 1.1 jtc it's impossible to reliably map timezone's arguments (a "minutes west
166 1.1 jtc of GMT" value and a "daylight saving time in effect" flag) to a
167 1.1 jtc time zone abbreviation, and we refuse to guess.
168 1.1 jtc Programs that in the past used the timezone function may now examine
169 1.1 jtc tzname[localtime(&clock)->tm_isdst] to learn the correct time
170 1.2 perry zone abbreviation to use. Alternatively, use
171 1.2 perry localtime(&clock)->tm_zone if this has been enabled.
172 1.2 perry
173 1.2 perry * The 4.2BSD gettimeofday function is not used in this package.
174 1.2 perry This formerly let users obtain the current UTC offset and DST flag,
175 1.2 perry but this functionality was removed in later versions of BSD.
176 1.1 jtc
177 1.2 perry * In SVR2, time conversion fails for near-minimum or near-maximum
178 1.3 jtc time_t values when doing conversions for places that don't use UTC.
179 1.2 perry This package takes care to do these conversions correctly.
180 1.2 perry
181 1.2 perry The functions that are conditionally compiled if STD_INSPIRED is defined
182 1.2 perry should, at this point, be looked on primarily as food for thought. They are
183 1.2 perry not in any sense "standard compatible"--some are not, in fact, specified in
184 1.2 perry *any* standard. They do, however, represent responses of various authors to
185 1.1 jtc standardization proposals.
186 1.1 jtc
187 1.1 jtc Other time conversion proposals, in particular the one developed by folks at
188 1.1 jtc Hewlett Packard, offer a wider selection of functions that provide capabilities
189 1.1 jtc beyond those provided here. The absence of such functions from this package
190 1.1 jtc is not meant to discourage the development, standardization, or use of such
191 1.1 jtc functions. Rather, their absence reflects the decision to make this package
192 1.9 mlelstv contain valid extensions to POSIX, to ensure its broad acceptability. If
193 1.9 mlelstv more powerful time conversion functions can be standardized, so much the
194 1.9 mlelstv better.
195 1.2 perry
196 1.2 perry
197 1.10 christos ----- Scope of the tz database -----
198 1.10 christos
199 1.10 christos The tz database attempts to record the history and predicted future of
200 1.10 christos all computer-based clocks that track civil time. To represent this
201 1.10 christos data, the world is partitioned into regions whose clocks all agree
202 1.10 christos about time stamps that occur after the somewhat-arbitrary cutoff point
203 1.10 christos of the POSIX Epoch (1970-01-01 00:00:00 UTC). For each such region,
204 1.10 christos the database records all known clock transitions, and labels the region
205 1.10 christos with a notable location.
206 1.10 christos
207 1.10 christos Clock transitions before 1970 are recorded for each such location,
208 1.10 christos because most POSIX-compatible systems support negative time stamps and
209 1.10 christos could misbehave if data were omitted for pre-1970 transitions.
210 1.10 christos However, the database is not designed for and does not suffice for
211 1.10 christos applications requiring accurate handling of all past times everywhere,
212 1.10 christos as it would take far too much effort and guesswork to record all
213 1.10 christos details of pre-1970 civil timekeeping.
214 1.10 christos
215 1.10 christos As noted in the README file, the tz database is not authoritative
216 1.10 christos (particularly not for pre-1970 time stamps), and it surely has errors.
217 1.10 christos Corrections are welcome and encouraged. Users requiring authoritative
218 1.10 christos data should consult national standards bodies and the references cited
219 1.10 christos in the database's comments.
220 1.10 christos
221 1.10 christos
222 1.2 perry ----- Names of time zone rule files -----
223 1.2 perry
224 1.6 kleink The time zone rule file naming conventions attempt to strike a balance
225 1.6 kleink among the following goals:
226 1.6 kleink
227 1.6 kleink * Uniquely identify every national region where clocks have all
228 1.6 kleink agreed since 1970. This is essential for the intended use: static
229 1.6 kleink clocks keeping local civil time.
230 1.6 kleink
231 1.6 kleink * Indicate to humans as to where that region is. This simplifes use.
232 1.6 kleink
233 1.6 kleink * Be robust in the presence of political changes. This reduces the
234 1.6 kleink number of updates and backward-compatibility hacks. For example,
235 1.6 kleink names of countries are ordinarily not used, to avoid
236 1.6 kleink incompatibilities when countries change their name
237 1.6 kleink (e.g. Zaire->Congo) or when locations change countries
238 1.6 kleink (e.g. Hong Kong from UK colony to China).
239 1.6 kleink
240 1.6 kleink * Be portable to a wide variety of implementations.
241 1.6 kleink This promotes use of the technology.
242 1.6 kleink
243 1.6 kleink * Use a consistent naming convention over the entire world.
244 1.6 kleink This simplifies both use and maintenance.
245 1.6 kleink
246 1.6 kleink This naming convention is not intended for use by inexperienced users
247 1.6 kleink to select TZ values by themselves (though they can of course examine
248 1.6 kleink and reuse existing settings). Distributors should provide
249 1.6 kleink documentation and/or a simple selection interface that explains the
250 1.6 kleink names; see the 'tzselect' program supplied with this distribution for
251 1.6 kleink one example.
252 1.2 perry
253 1.2 perry Names normally have the form AREA/LOCATION, where AREA is the name
254 1.2 perry of a continent or ocean, and LOCATION is the name of a specific
255 1.2 perry location within that region. North and South America share the same
256 1.2 perry area, `America'. Typical names are `Africa/Cairo', `America/New_York',
257 1.2 perry and `Pacific/Honolulu'.
258 1.2 perry
259 1.2 perry Here are the general rules used for choosing location names,
260 1.2 perry in decreasing order of importance:
261 1.2 perry
262 1.6 kleink Use only valid POSIX file name components (i.e., the parts of
263 1.6 kleink names other than `/'). Within a file name component,
264 1.6 kleink use only ASCII letters, `.', `-' and `_'. Do not use
265 1.6 kleink digits, as that might create an ambiguity with POSIX
266 1.6 kleink TZ strings. A file name component must not exceed 14
267 1.6 kleink characters or start with `-'. E.g., prefer `Brunei'
268 1.6 kleink to `Bandar_Seri_Begawan'.
269 1.2 perry Include at least one location per time zone rule set per country.
270 1.5 kleink One such location is enough. Use ISO 3166 (see the file
271 1.5 kleink iso3166.tab) to help decide whether something is a country.
272 1.9 mlelstv However, uninhabited ISO 3166 regions like Bouvet Island
273 1.9 mlelstv do not need locations, since local time is not defined there.
274 1.2 perry If all the clocks in a country's region have agreed since 1970,
275 1.2 perry don't bother to include more than one location
276 1.2 perry even if subregions' clocks disagreed before 1970.
277 1.2 perry Otherwise these tables would become annoyingly large.
278 1.2 perry If a name is ambiguous, use a less ambiguous alternative;
279 1.2 perry e.g. many cities are named San Jose and Georgetown, so
280 1.2 perry prefer `Costa_Rica' to `San_Jose' and `Guyana' to `Georgetown'.
281 1.2 perry Keep locations compact. Use cities or small islands, not countries
282 1.2 perry or regions, so that any future time zone changes do not split
283 1.2 perry locations into different time zones. E.g. prefer `Paris'
284 1.2 perry to `France', since France has had multiple time zones.
285 1.6 kleink Use mainstream English spelling, e.g. prefer `Rome' to `Roma', and
286 1.2 perry prefer `Athens' to the true name (which uses Greek letters).
287 1.6 kleink The POSIX file name restrictions encourage this rule.
288 1.2 perry Use the most populous among locations in a country's time zone,
289 1.2 perry e.g. prefer `Shanghai' to `Beijing'. Among locations with
290 1.2 perry similar populations, pick the best-known location,
291 1.2 perry e.g. prefer `Rome' to `Milan'.
292 1.2 perry Use the singular form, e.g. prefer `Canary' to `Canaries'.
293 1.2 perry Omit common suffixes like `_Islands' and `_City', unless that
294 1.2 perry would lead to ambiguity. E.g. prefer `Cayman' to
295 1.2 perry `Cayman_Islands' and `Guatemala' to `Guatemala_City',
296 1.2 perry but prefer `Mexico_City' to `Mexico' because the country
297 1.2 perry of Mexico has several time zones.
298 1.2 perry Use `_' to represent a space.
299 1.2 perry Omit `.' from abbreviations in names, e.g. prefer `St_Helena'
300 1.2 perry to `St._Helena'.
301 1.5 kleink Do not change established names if they only marginally
302 1.5 kleink violate the above rules. For example, don't change
303 1.5 kleink the existing name `Rome' to `Milan' merely because
304 1.5 kleink Milan's population has grown to be somewhat greater
305 1.5 kleink than Rome's.
306 1.5 kleink If a name is changed, put its old spelling in the `backward' file.
307 1.2 perry
308 1.2 perry The file `zone.tab' lists the geographical locations used to name
309 1.9 mlelstv time zone rule files. It is intended to be an exhaustive list
310 1.9 mlelstv of canonical names for geographic regions.
311 1.2 perry
312 1.2 perry Older versions of this package used a different naming scheme,
313 1.2 perry and these older names are still supported.
314 1.5 kleink See the file `backward' for most of these older names
315 1.2 perry (e.g. `US/Eastern' instead of `America/New_York').
316 1.2 perry The other old-fashioned names still supported are
317 1.10 christos +`WET', `CET', `MET', and `EET' (see the file `europe').
318 1.2 perry
319 1.2 perry
320 1.2 perry ----- Time zone abbreviations -----
321 1.2 perry
322 1.2 perry When this package is installed, it generates time zone abbreviations
323 1.9 mlelstv like `EST' to be compatible with human tradition and POSIX.
324 1.2 perry Here are the general rules used for choosing time zone abbreviations,
325 1.2 perry in decreasing order of importance:
326 1.2 perry
327 1.6 kleink Use abbreviations that consist of three or more ASCII letters.
328 1.2 perry Previous editions of this database also used characters like
329 1.2 perry ' ' and '?', but these characters have a special meaning to
330 1.2 perry the shell and cause commands like
331 1.2 perry set `date`
332 1.6 kleink to have unexpected effects.
333 1.6 kleink Previous editions of this rule required upper-case letters,
334 1.6 kleink but the Congressman who introduced Chamorro Standard Time
335 1.6 kleink preferred "ChST", so the rule has been relaxed.
336 1.6 kleink
337 1.6 kleink This rule guarantees that all abbreviations could have
338 1.9 mlelstv been specified by a POSIX TZ string. POSIX
339 1.6 kleink requires at least three characters for an
340 1.9 mlelstv abbreviation. POSIX through 2000 says that an abbreviation
341 1.6 kleink cannot start with ':', and cannot contain ',', '-',
342 1.9 mlelstv '+', NUL, or a digit. POSIX from 2001 on changes this
343 1.9 mlelstv rule to say that an abbreviation can contain only '-', '+',
344 1.9 mlelstv and alphanumeric characters from the portable character set
345 1.9 mlelstv in the current locale. To be portable to both sets of
346 1.6 kleink rules, an abbreviation must therefore use only ASCII
347 1.9 mlelstv letters.
348 1.6 kleink
349 1.2 perry Use abbreviations that are in common use among English-speakers,
350 1.2 perry e.g. `EST' for Eastern Standard Time in North America.
351 1.2 perry We assume that applications translate them to other languages
352 1.2 perry as part of the normal localization process; for example,
353 1.2 perry a French application might translate `EST' to `HNE'.
354 1.6 kleink
355 1.2 perry For zones whose times are taken from a city's longitude, use the
356 1.2 perry traditional xMT notation, e.g. `PMT' for Paris Mean Time.
357 1.2 perry The only name like this in current use is `GMT'.
358 1.6 kleink
359 1.2 perry If there is no common English abbreviation, abbreviate the English
360 1.2 perry translation of the usual phrase used by native speakers.
361 1.2 perry If this is not available or is a phrase mentioning the country
362 1.2 perry (e.g. ``Cape Verde Time''), then:
363 1.2 perry
364 1.2 perry When a country has a single or principal time zone region,
365 1.2 perry append `T' to the country's ISO code, e.g. `CVT' for
366 1.2 perry Cape Verde Time. For summer time append `ST';
367 1.2 perry for double summer time append `DST'; etc.
368 1.2 perry When a country has multiple time zones, take the first three
369 1.2 perry letters of an English place name identifying each zone
370 1.2 perry and then append `T', `ST', etc. as before;
371 1.2 perry e.g. `VLAST' for VLAdivostok Summer Time.
372 1.2 perry
373 1.9 mlelstv Use UTC (with time zone abbreviation "zzz") for locations while
374 1.9 mlelstv uninhabited. The "zzz" mnemonic is that these locations are,
375 1.9 mlelstv in some sense, asleep.
376 1.6 kleink
377 1.2 perry Application writers should note that these abbreviations are ambiguous
378 1.2 perry in practice: e.g. `EST' has a different meaning in Australia than
379 1.2 perry it does in the United States. In new applications, it's often better
380 1.3 jtc to use numeric UTC offsets like `-0500' instead of time zone
381 1.2 perry abbreviations like `EST'; this avoids the ambiguity.
382 1.4 kleink
383 1.4 kleink
384 1.4 kleink ----- Calendrical issues -----
385 1.4 kleink
386 1.4 kleink Calendrical issues are a bit out of scope for a time zone database,
387 1.4 kleink but they indicate the sort of problems that we would run into if we
388 1.4 kleink extended the time zone database further into the past. An excellent
389 1.10 christos resource in this area is Nachum Dershowitz and Edward M. Reingold,
390 1.10 christos <a href="http://emr.cs.iit.edu/home/reingold/calendar-book/third-edition/">
391 1.10 christos Calendrical Calculations: Third Edition
392 1.10 christos </a>, Cambridge University Press (2008). Other information and
393 1.4 kleink sources are given below. They sometimes disagree.
394 1.4 kleink
395 1.4 kleink
396 1.4 kleink France
397 1.4 kleink
398 1.4 kleink Gregorian calendar adopted 1582-12-20.
399 1.4 kleink French Revolutionary calendar used 1793-11-24 through 1805-12-31,
400 1.4 kleink and (in Paris only) 1871-05-06 through 1871-05-23.
401 1.4 kleink
402 1.4 kleink
403 1.4 kleink Russia
404 1.4 kleink
405 1.9 mlelstv From Chris Carrier (1996-12-02):
406 1.4 kleink On 1929-10-01 the Soviet Union instituted an ``Eternal Calendar''
407 1.4 kleink with 30-day months plus 5 holidays, with a 5-day week.
408 1.4 kleink On 1931-12-01 it changed to a 6-day week; in 1934 it reverted to the
409 1.4 kleink Gregorian calendar while retaining the 6-day week; on 1940-06-27 it
410 1.4 kleink reverted to the 7-day week. With the 6-day week the usual days
411 1.4 kleink off were the 6th, 12th, 18th, 24th and 30th of the month.
412 1.4 kleink (Source: Evitiar Zerubavel, _The Seven Day Circle_)
413 1.4 kleink
414 1.4 kleink
415 1.4 kleink Mark Brader reported a similar story in "The Book of Calendars", edited
416 1.4 kleink by Frank Parise (1982, Facts on File, ISBN 0-8719-6467-8), page 377. But:
417 1.4 kleink
418 1.4 kleink From: Petteri Sulonen (via Usenet)
419 1.4 kleink Date: 14 Jan 1999 00:00:00 GMT
420 1.9 mlelstv ...
421 1.4 kleink
422 1.4 kleink If your source is correct, how come documents between 1929 -- 1940 were
423 1.4 kleink still dated using the conventional, Gregorian calendar?
424 1.4 kleink
425 1.4 kleink I can post a scan of a document dated December 1, 1934, signed by
426 1.4 kleink Yenukidze, the secretary, on behalf of Kalinin, the President of the
427 1.4 kleink Executive Committee of the Supreme Soviet, if you like.
428 1.4 kleink
429 1.4 kleink
430 1.4 kleink
431 1.4 kleink Sweden (and Finland)
432 1.4 kleink
433 1.9 mlelstv From: Mark Brader
434 1.4 kleink <a href="news:1996Jul6.012937.29190 (a] sq.com">
435 1.4 kleink Subject: Re: Gregorian reform -- a part of locale?
436 1.4 kleink </a>
437 1.4 kleink Date: 1996-07-06
438 1.4 kleink
439 1.4 kleink In 1700, Denmark made the transition from Julian to Gregorian. Sweden
440 1.4 kleink decided to *start* a transition in 1700 as well, but rather than have one of
441 1.4 kleink those unsightly calendar gaps :-), they simply decreed that the next leap
442 1.4 kleink year after 1696 would be in 1744 -- putting the whole country on a calendar
443 1.4 kleink different from both Julian and Gregorian for a period of 40 years.
444 1.4 kleink
445 1.4 kleink However, in 1704 something went wrong and the plan was not carried through;
446 1.4 kleink they did, after all, have a leap year that year. And one in 1708. In 1712
447 1.4 kleink they gave it up and went back to Julian, putting 30 days in February that
448 1.4 kleink year!...
449 1.4 kleink
450 1.4 kleink Then in 1753, Sweden made the transition to Gregorian in the usual manner,
451 1.4 kleink getting there only 13 years behind the original schedule.
452 1.4 kleink
453 1.4 kleink (A previous posting of this story was challenged, and Swedish readers
454 1.4 kleink produced the following references to support it: "Tiderakning och historia"
455 1.4 kleink by Natanael Beckman (1924) and "Tid, en bok om tiderakning och
456 1.4 kleink kalendervasen" by Lars-Olof Lode'n (no date was given).)
457 1.4 kleink
458 1.4 kleink
459 1.4 kleink Grotefend's data
460 1.4 kleink
461 1.9 mlelstv From: "Michael Palmer" [with one obvious typo fixed]
462 1.4 kleink Subject: Re: Gregorian Calendar (was Re: Another FHC related question
463 1.4 kleink Newsgroups: soc.genealogy.german
464 1.4 kleink Date: Tue, 9 Feb 1999 02:32:48 -800
465 1.9 mlelstv ...
466 1.4 kleink
467 1.6 kleink The following is a(n incomplete) listing, arranged chronologically, of
468 1.6 kleink European states, with the date they converted from the Julian to the
469 1.4 kleink Gregorian calendar:
470 1.4 kleink
471 1.4 kleink 04/15 Oct 1582 - Italy (with exceptions), Spain, Portugal, Poland (Roman
472 1.4 kleink Catholics and Danzig only)
473 1.4 kleink 09/20 Dec 1582 - France, Lorraine
474 1.4 kleink
475 1.4 kleink 21 Dec 1582/
476 1.4 kleink 01 Jan 1583 - Holland, Brabant, Flanders, Hennegau
477 1.4 kleink 10/21 Feb 1583 - bishopric of Liege (L"uttich)
478 1.4 kleink 13/24 Feb 1583 - bishopric of Augsburg
479 1.4 kleink 04/15 Oct 1583 - electorate of Trier
480 1.4 kleink 05/16 Oct 1583 - Bavaria, bishoprics of Freising, Eichstedt, Regensburg,
481 1.4 kleink Salzburg, Brixen
482 1.4 kleink 13/24 Oct 1583 - Austrian Oberelsass and Breisgau
483 1.4 kleink 20/31 Oct 1583 - bishopric of Basel
484 1.4 kleink 02/13 Nov 1583 - duchy of J"ulich-Berg
485 1.4 kleink 02/13 Nov 1583 - electorate and city of K"oln
486 1.4 kleink 04/15 Nov 1583 - bishopric of W"urzburg
487 1.4 kleink 11/22 Nov 1583 - electorate of Mainz
488 1.4 kleink 16/27 Nov 1583 - bishopric of Strassburg and the margraviate of Baden
489 1.4 kleink 17/28 Nov 1583 - bishopric of M"unster and duchy of Cleve
490 1.4 kleink 14/25 Dec 1583 - Steiermark
491 1.4 kleink
492 1.4 kleink 06/17 Jan 1584 - Austria and Bohemia
493 1.4 kleink 11/22 Jan 1584 - Luzern, Uri, Schwyz, Zug, Freiburg, Solothurn
494 1.4 kleink 12/23 Jan 1584 - Silesia and the Lausitz
495 1.4 kleink 22 Jan/
496 1.4 kleink 02 Feb 1584 - Hungary (legally on 21 Oct 1587)
497 1.4 kleink Jun 1584 - Unterwalden
498 1.4 kleink 01/12 Jul 1584 - duchy of Westfalen
499 1.4 kleink
500 1.4 kleink 16/27 Jun 1585 - bishopric of Paderborn
501 1.4 kleink
502 1.4 kleink 14/25 Dec 1590 - Transylvania
503 1.4 kleink
504 1.4 kleink 22 Aug/
505 1.4 kleink 02 Sep 1612 - duchy of Prussia
506 1.4 kleink
507 1.4 kleink 13/24 Dec 1614 - Pfalz-Neuburg
508 1.4 kleink
509 1.4 kleink 1617 - duchy of Kurland (reverted to the Julian calendar in
510 1.4 kleink 1796)
511 1.4 kleink
512 1.4 kleink 1624 - bishopric of Osnabr"uck
513 1.4 kleink
514 1.4 kleink 1630 - bishopric of Minden
515 1.4 kleink
516 1.4 kleink 15/26 Mar 1631 - bishopric of Hildesheim
517 1.4 kleink
518 1.4 kleink 1655 - Kanton Wallis
519 1.4 kleink
520 1.4 kleink 05/16 Feb 1682 - city of Strassburg
521 1.4 kleink
522 1.4 kleink 18 Feb/
523 1.4 kleink 01 Mar 1700 - Protestant Germany (including Swedish possessions in
524 1.4 kleink Germany), Denmark, Norway
525 1.4 kleink 30 Jun/
526 1.4 kleink 12 Jul 1700 - Gelderland, Zutphen
527 1.4 kleink 10 Nov/
528 1.4 kleink 12 Dec 1700 - Utrecht, Overijssel
529 1.4 kleink
530 1.4 kleink 31 Dec 1700/
531 1.4 kleink 12 Jan 1701 - Friesland, Groningen, Z"urich, Bern, Basel, Geneva,
532 1.4 kleink Turgau, and Schaffhausen
533 1.4 kleink
534 1.4 kleink 1724 - Glarus, Appenzell, and the city of St. Gallen
535 1.4 kleink
536 1.4 kleink 01 Jan 1750 - Pisa and Florence
537 1.4 kleink
538 1.4 kleink 02/14 Sep 1752 - Great Britain
539 1.4 kleink
540 1.4 kleink 17 Feb/
541 1.4 kleink 01 Mar 1753 - Sweden
542 1.4 kleink
543 1.4 kleink 1760-1812 - Graub"unden
544 1.4 kleink
545 1.6 kleink The Russian empire (including Finland and the Baltic states) did not
546 1.4 kleink convert to the Gregorian calendar until the Soviet revolution of 1917.
547 1.4 kleink
548 1.6 kleink Source: H. Grotefend, _Taschenbuch der Zeitrechnung des deutschen
549 1.6 kleink Mittelalters und der Neuzeit_, herausgegeben von Dr. O. Grotefend
550 1.4 kleink (Hannover: Hahnsche Buchhandlung, 1941), pp. 26-28.
551 1.8 kleink
552 1.8 kleink
553 1.8 kleink ----- Time and time zones on Mars -----
554 1.8 kleink
555 1.8 kleink Some people have adjusted their work schedules to fit Mars time.
556 1.8 kleink Dozens of special Mars watches were built for Jet Propulsion
557 1.8 kleink Laboratory workers who kept Mars time during the Mars Exploration
558 1.8 kleink Rovers mission (2004). These timepieces look like normal Seikos and
559 1.8 kleink Citizens but use Mars seconds rather than terrestrial seconds.
560 1.8 kleink
561 1.8 kleink A Mars solar day is called a "sol" and has a mean period equal to
562 1.8 kleink about 24 hours 39 minutes 35.244 seconds in terrestrial time. It is
563 1.8 kleink divided into a conventional 24-hour clock, so each Mars second equals
564 1.8 kleink about 1.02749125 terrestrial seconds.
565 1.8 kleink
566 1.8 kleink The prime meridian of Mars goes through the center of the crater
567 1.8 kleink Airy-0, named in honor of the British astronomer who built the
568 1.8 kleink Greenwich telescope that defines Earth's prime meridian. Mean solar
569 1.8 kleink time on the Mars prime meridian is called Mars Coordinated Time (MTC).
570 1.8 kleink
571 1.8 kleink Each landed mission on Mars has adopted a different reference for
572 1.8 kleink solar time keeping, so there is no real standard for Mars time zones.
573 1.8 kleink For example, the Mars Exploration Rover project (2004) defined two
574 1.8 kleink time zones "Local Solar Time A" and "Local Solar Time B" for its two
575 1.8 kleink missions, each zone designed so that its time equals local true solar
576 1.8 kleink time at approximately the middle of the nominal mission. Such a "time
577 1.8 kleink zone" is not particularly suited for any application other than the
578 1.8 kleink mission itself.
579 1.8 kleink
580 1.8 kleink Many calendars have been proposed for Mars, but none have achieved
581 1.8 kleink wide acceptance. Astronomers often use Mars Sol Date (MSD) which is a
582 1.8 kleink sequential count of Mars solar days elapsed since about 1873-12-29
583 1.8 kleink 12:00 GMT.
584 1.8 kleink
585 1.8 kleink The tz database does not currently support Mars time, but it is
586 1.8 kleink documented here in the hopes that support will be added eventually.
587 1.8 kleink
588 1.8 kleink Sources:
589 1.8 kleink
590 1.8 kleink Michael Allison and Robert Schmunk,
591 1.8 kleink "Technical Notes on Mars Solar Time as Adopted by the Mars24 Sunclock"
592 1.9 mlelstv <http://www.giss.nasa.gov/tools/mars24/help/notes.html> (2004-07-30).
593 1.8 kleink
594 1.8 kleink Jia-Rui Chong, "Workdays Fit for a Martian", Los Angeles Times
595 1.8 kleink (2004-01-14), pp A1, A20-A21.
596