diff --git a/external/public-domain/tz/dist/TZDATA_VERSION b/external/public-domain/tz/dist/TZDATA_VERSION
index b9b6b8d106cb..5ec975e59eec 100644
--- a/external/public-domain/tz/dist/TZDATA_VERSION
+++ b/external/public-domain/tz/dist/TZDATA_VERSION
@@ -1 +1 @@
-tzdata-2017b
+tzdata-2017c
diff --git a/external/public-domain/tz/dist/Theory b/external/public-domain/tz/dist/Theory
deleted file mode 100644
index 33e46069ba23..000000000000
--- a/external/public-domain/tz/dist/Theory
+++ /dev/null
@@ -1,870 +0,0 @@
-Theory and pragmatics of the tz code and data
-
-
------ Outline -----
-
- Scope of the tz database
- Names of time zone rules
- Time zone abbreviations
- Accuracy of the tz database
- Time and date functions
- Interface stability
- Calendrical issues
- Time and time zones on Mars
-
-
------ Scope of the tz database -----
-
-The tz database attempts to record the history and predicted future of
-all computer-based clocks that track civil time. To represent this
-data, the world is partitioned into regions whose clocks all agree
-about time stamps that occur after the somewhat-arbitrary cutoff point
-of the POSIX Epoch (1970-01-01 00:00:00 UTC). For each such region,
-the database records all known clock transitions, and labels the region
-with a notable location. Although 1970 is a somewhat-arbitrary
-cutoff, there are significant challenges to moving the cutoff earlier
-even by a decade or two, due to the wide variety of local practices
-before computer timekeeping became prevalent.
-
-Clock transitions before 1970 are recorded for each such location,
-because most systems support time stamps before 1970 and could
-misbehave if data entries were omitted for pre-1970 transitions.
-However, the database is not designed for and does not suffice for
-applications requiring accurate handling of all past times everywhere,
-as it would take far too much effort and guesswork to record all
-details of pre-1970 civil timekeeping.
-
-As described below, reference source code for using the tz database is
-also available. The tz code is upwards compatible with POSIX, an
-international standard for UNIX-like systems. As of this writing, the
-current edition of POSIX is:
-
- The Open Group Base Specifications Issue 7
- IEEE Std 1003.1-2008, 2016 Edition
-
-
-
-
------ Names of time zone rules -----
-
-Each of the database's time zone rules has a unique name.
-Inexperienced users are not expected to select these names unaided.
-Distributors should provide documentation and/or a simple selection
-interface that explains the names; for one example, see the 'tzselect'
-program in the tz code. The Unicode Common Locale Data Repository
- contains data that may be useful for other
-selection interfaces.
-
-The time zone rule naming conventions attempt to strike a balance
-among the following goals:
-
- * Uniquely identify every region where clocks have agreed since 1970.
- This is essential for the intended use: static clocks keeping local
- civil time.
-
- * Indicate to experts where that region is.
-
- * Be robust in the presence of political changes. For example, names
- of countries are ordinarily not used, to avoid incompatibilities
- when countries change their name (e.g. Zaire->Congo) or when
- locations change countries (e.g. Hong Kong from UK colony to
- China).
-
- * Be portable to a wide variety of implementations.
-
- * Use a consistent naming conventions over the entire world.
-
-Names normally have the form AREA/LOCATION, where AREA is the name
-of a continent or ocean, and LOCATION is the name of a specific
-location within that region. North and South America share the same
-area, 'America'. Typical names are 'Africa/Cairo', 'America/New_York',
-and 'Pacific/Honolulu'.
-
-Here are the general rules used for choosing location names,
-in decreasing order of importance:
-
- Use only valid POSIX file name components (i.e., the parts of
- names other than '/'). Do not use the file name
- components '.' and '..'. Within a file name component,
- use only ASCII letters, '.', '-' and '_'. Do not use
- digits, as that might create an ambiguity with POSIX
- TZ strings. A file name component must not exceed 14
- characters or start with '-'. E.g., prefer 'Brunei'
- to 'Bandar_Seri_Begawan'. Exceptions: see the discussion
- of legacy names below.
- A name must not be empty, or contain '//', or start or end with '/'.
- Do not use names that differ only in case. Although the reference
- implementation is case-sensitive, some other implementations
- are not, and they would mishandle names differing only in case.
- If one name A is an initial prefix of another name AB (ignoring case),
- then B must not start with '/', as a regular file cannot have
- the same name as a directory in POSIX. For example,
- 'America/New_York' precludes 'America/New_York/Bronx'.
- Uninhabited regions like the North Pole and Bouvet Island
- do not need locations, since local time is not defined there.
- There should typically be at least one name for each ISO 3166-1
- officially assigned two-letter code for an inhabited country
- or territory.
- If all the clocks in a region have agreed since 1970,
- don't bother to include more than one location
- even if subregions' clocks disagreed before 1970.
- Otherwise these tables would become annoyingly large.
- If a name is ambiguous, use a less ambiguous alternative;
- e.g. many cities are named San José and Georgetown, so
- prefer 'Costa_Rica' to 'San_Jose' and 'Guyana' to 'Georgetown'.
- Keep locations compact. Use cities or small islands, not countries
- or regions, so that any future time zone changes do not split
- locations into different time zones. E.g. prefer 'Paris'
- to 'France', since France has had multiple time zones.
- Use mainstream English spelling, e.g. prefer 'Rome' to 'Roma', and
- prefer 'Athens' to the Greek 'Αθήνα' or the Romanized 'Athína'.
- The POSIX file name restrictions encourage this rule.
- Use the most populous among locations in a zone,
- e.g. prefer 'Shanghai' to 'Beijing'. Among locations with
- similar populations, pick the best-known location,
- e.g. prefer 'Rome' to 'Milan'.
- Use the singular form, e.g. prefer 'Canary' to 'Canaries'.
- Omit common suffixes like '_Islands' and '_City', unless that
- would lead to ambiguity. E.g. prefer 'Cayman' to
- 'Cayman_Islands' and 'Guatemala' to 'Guatemala_City',
- but prefer 'Mexico_City' to 'Mexico' because the country
- of Mexico has several time zones.
- Use '_' to represent a space.
- Omit '.' from abbreviations in names, e.g. prefer 'St_Helena'
- to 'St._Helena'.
- Do not change established names if they only marginally
- violate the above rules. For example, don't change
- the existing name 'Rome' to 'Milan' merely because
- Milan's population has grown to be somewhat greater
- than Rome's.
- If a name is changed, put its old spelling in the 'backward' file.
- This means old spellings will continue to work.
-
-The file 'zone1970.tab' lists geographical locations used to name time
-zone rules. It is intended to be an exhaustive list of names for
-geographic regions as described above; this is a subset of the names
-in the data. Although a 'zone1970.tab' location's longitude
-corresponds to its LMT offset with one hour for every 15 degrees east
-longitude, this relationship is not exact.
-
-Older versions of this package used a different naming scheme,
-and these older names are still supported.
-See the file 'backward' for most of these older names
-(e.g., 'US/Eastern' instead of 'America/New_York').
-The other old-fashioned names still supported are
-'WET', 'CET', 'MET', and 'EET' (see the file 'europe').
-
-Older versions of this package defined legacy names that are
-incompatible with the first rule of location names, but which are
-still supported. These legacy names are mostly defined in the file
-'etcetera'. Also, the file 'backward' defines the legacy names
-'GMT0', 'GMT-0', 'GMT+0' and 'Canada/East-Saskatchewan', and the file
-'northamerica' defines the legacy names 'EST5EDT', 'CST6CDT',
-'MST7MDT', and 'PST8PDT'.
-
-Excluding 'backward' should not affect the other data. If
-'backward' is excluded, excluding 'etcetera' should not affect the
-remaining data.
-
-
------ Time zone abbreviations -----
-
-When this package is installed, it generates time zone abbreviations
-like 'EST' to be compatible with human tradition and POSIX.
-Here are the general rules used for choosing time zone abbreviations,
-in decreasing order of importance:
-
- Use three or more characters that are ASCII alphanumerics or '+' or '-'.
- Previous editions of this database also used characters like
- ' ' and '?', but these characters have a special meaning to
- the shell and cause commands like
- set `date`
- to have unexpected effects.
- Previous editions of this rule required upper-case letters,
- but the Congressman who introduced Chamorro Standard Time
- preferred "ChST", so lower-case letters are now allowed.
- Also, POSIX from 2001 on relaxed the rule to allow '-', '+',
- and alphanumeric characters from the portable character set
- in the current locale. In practice ASCII alphanumerics and
- '+' and '-' are safe in all locales.
-
- In other words, in the C locale the POSIX extended regular
- expression [-+[:alnum:]]{3,} should match the abbreviation.
- This guarantees that all abbreviations could have been
- specified by a POSIX TZ string.
-
- Use abbreviations that are in common use among English-speakers,
- e.g. 'EST' for Eastern Standard Time in North America.
- We assume that applications translate them to other languages
- as part of the normal localization process; for example,
- a French application might translate 'EST' to 'HNE'.
-
- For zones whose times are taken from a city's longitude, use the
- traditional xMT notation, e.g. 'PMT' for Paris Mean Time.
- The only name like this in current use is 'GMT'.
-
- Use 'LMT' for local mean time of locations before the introduction
- of standard time; see "Scope of the tz database".
-
- If there is no common English abbreviation, use numeric offsets like
- -05 and +0830 that are generated by zic's %z notation.
-
- Use current abbreviations for older timestamps to avoid confusion.
- For example, in 1910 a common English abbreviation for UT +01
- in central Europe was 'MEZ' (short for both "Middle European
- Zone" and for "Mitteleuropäische Zeit" in German). Nowadays
- 'CET' ("Central European Time") is more common in English, and
- the database uses 'CET' even for circa-1910 timestamps as this
- is less confusing for modern users and avoids the need for
- determining when 'CET' supplanted 'MEZ' in common usage.
-
- Use a consistent style in a zone's history. For example, if a zone's
- history tends to use numeric abbreviations and a particular
- entry could go either way, use a numeric abbreviation.
-
- [The remaining guidelines predate the introduction of %z.
- They are problematic as they mean tz data entries invent
- notation rather than record it. These guidelines are now
- deprecated and the plan is to gradually move to %z for
- inhabited locations and to "-00" for uninhabited locations.]
-
- If there is no common English abbreviation, abbreviate the English
- translation of the usual phrase used by native speakers.
- If this is not available or is a phrase mentioning the country
- (e.g. "Cape Verde Time"), then:
-
- When a country is identified with a single or principal zone,
- append 'T' to the country's ISO code, e.g. 'CVT' for
- Cape Verde Time. For summer time append 'ST';
- for double summer time append 'DST'; etc.
- Otherwise, take the first three letters of an English place
- name identifying each zone and append 'T', 'ST', etc.
- as before; e.g. 'CHAST' for CHAtham Summer Time.
-
- Use UT (with time zone abbreviation '-00') for locations while
- uninhabited. The leading '-' is a flag that the time
- zone is in some sense undefined; this notation is
- derived from Internet RFC 3339.
-
-Application writers should note that these abbreviations are ambiguous
-in practice: e.g. 'CST' has a different meaning in China than
-it does in the United States. In new applications, it's often better
-to use numeric UT offsets like '-0600' instead of time zone
-abbreviations like 'CST'; this avoids the ambiguity.
-
-
------ Accuracy of the tz database -----
-
-The tz database is not authoritative, and it surely has errors.
-Corrections are welcome and encouraged; see the file CONTRIBUTING.
-Users requiring authoritative data should consult national standards
-bodies and the references cited in the database's comments.
-
-Errors in the tz database arise from many sources:
-
- * The tz database predicts future time stamps, and current predictions
- will be incorrect after future governments change the rules.
- For example, if today someone schedules a meeting for 13:00 next
- October 1, Casablanca time, and tomorrow Morocco changes its
- daylight saving rules, software can mess up after the rule change
- if it blithely relies on conversions made before the change.
-
- * The pre-1970 entries in this database cover only a tiny sliver of how
- clocks actually behaved; the vast majority of the necessary
- information was lost or never recorded. Thousands more zones would
- be needed if the tz database's scope were extended to cover even
- just the known or guessed history of standard time; for example,
- the current single entry for France would need to split into dozens
- of entries, perhaps hundreds. And in most of the world even this
- approach would be misleading due to widespread disagreement or
- indifference about what times should be observed. In her 2015 book
- "The Global Transformation of Time, 1870-1950", Vanessa Ogle writes
- "Outside of Europe and North America there was no system of time
- zones at all, often not even a stable landscape of mean times,
- prior to the middle decades of the twentieth century". See:
- Timothy Shenk, Booked: A Global History of Time. Dissent 2015-12-17
- https://www.dissentmagazine.org/blog/booked-a-global-history-of-time-vanessa-ogle
-
- * Most of the pre-1970 data entries come from unreliable sources, often
- astrology books that lack citations and whose compilers evidently
- invented entries when the true facts were unknown, without
- reporting which entries were known and which were invented.
- These books often contradict each other or give implausible entries,
- and on the rare occasions when they are checked they are
- typically found to be incorrect.
-
- * For the UK the tz database relies on years of first-class work done by
- Joseph Myers and others; see .
- Other countries are not done nearly as well.
-
- * Sometimes, different people in the same city would maintain clocks
- that differed significantly. Railway time was used by railroad
- companies (which did not always agree with each other),
- church-clock time was used for birth certificates, etc.
- Often this was merely common practice, but sometimes it was set by law.
- For example, from 1891 to 1911 the UT offset in France was legally
- 0:09:21 outside train stations and 0:04:21 inside.
-
- * Although a named location in the tz database stands for the
- containing region, its pre-1970 data entries are often accurate for
- only a small subset of that region. For example, Europe/London
- stands for the United Kingdom, but its pre-1847 times are valid
- only for locations that have London's exact meridian, and its 1847
- transition to GMT is known to be valid only for the L&NW and the
- Caledonian railways.
-
- * The tz database does not record the earliest time for which a zone's
- data entries are thereafter valid for every location in the region.
- For example, Europe/London is valid for all locations in its
- region after GMT was made the standard time, but the date of
- standardization (1880-08-02) is not in the tz database, other than
- in commentary. For many zones the earliest time of validity is
- unknown.
-
- * The tz database does not record a region's boundaries, and in many
- cases the boundaries are not known. For example, the zone
- America/Kentucky/Louisville represents a region around the city of
- Louisville, the boundaries of which are unclear.
-
- * Changes that are modeled as instantaneous transitions in the tz
- database were often spread out over hours, days, or even decades.
-
- * Even if the time is specified by law, locations sometimes
- deliberately flout the law.
-
- * Early timekeeping practices, even assuming perfect clocks, were
- often not specified to the accuracy that the tz database requires.
-
- * Sometimes historical timekeeping was specified more precisely
- than what the tz database can handle. For example, from 1909 to
- 1937 Netherlands clocks were legally UT +00:19:32.13, but the tz
- database cannot represent the fractional second.
-
- * Even when all the timestamp transitions recorded by the tz database
- are correct, the tz rules that generate them may not faithfully
- reflect the historical rules. For example, from 1922 until World
- War II the UK moved clocks forward the day following the third
- Saturday in April unless that was Easter, in which case it moved
- clocks forward the previous Sunday. Because the tz database has no
- way to specify Easter, these exceptional years are entered as
- separate tz Rule lines, even though the legal rules did not change.
-
- * The tz database models pre-standard time using the proleptic Gregorian
- calendar and local mean time (LMT), but many people used other
- calendars and other timescales. For example, the Roman Empire used
- the Julian calendar, and had 12 varying-length daytime hours with a
- non-hour-based system at night.
-
- * Early clocks were less reliable, and data entries do not represent
- clock error.
-
- * The tz database assumes Universal Time (UT) as an origin, even
- though UT is not standardized for older time stamps. In the tz
- database commentary, UT denotes a family of time standards that
- includes Coordinated Universal Time (UTC) along with other variants
- such as UT1 and GMT, with days starting at midnight. Although UT
- equals UTC for modern time stamps, UTC was not defined until 1960,
- so commentary uses the more-general abbreviation UT for time stamps
- that might predate 1960. Since UT, UT1, etc. disagree slightly,
- and since pre-1972 UTC seconds varied in length, interpretation of
- older time stamps can be problematic when subsecond accuracy is
- needed.
-
- * Civil time was not based on atomic time before 1972, and we don't
- know the history of earth's rotation accurately enough to map SI
- seconds to historical solar time to more than about one-hour
- accuracy. See: Stephenson FR, Morrison LV, Hohenkerk CY.
- Measurement of the Earth's rotation: 720 BC to AD 2015.
- Proc Royal Soc A. 2016 Dec 7;472:20160404.
- http://dx.doi.org/10.1098/rspa.2016.0404
- Also see: Espenak F. Uncertainty in Delta T (ΔT).
- http://eclipse.gsfc.nasa.gov/SEhelp/uncertainty2004.html
-
- * The relationship between POSIX time (that is, UTC but ignoring leap
- seconds) and UTC is not agreed upon after 1972. Although the POSIX
- clock officially stops during an inserted leap second, at least one
- proposed standard has it jumping back a second instead; and in
- practice POSIX clocks more typically either progress glacially during
- a leap second, or are slightly slowed while near a leap second.
-
- * The tz database does not represent how uncertain its information is.
- Ideally it would contain information about when data entries are
- incomplete or dicey. Partial temporal knowledge is a field of
- active research, though, and it's not clear how to apply it here.
-
-In short, many, perhaps most, of the tz database's pre-1970 and future
-time stamps are either wrong or misleading. Any attempt to pass the
-tz database off as the definition of time should be unacceptable to
-anybody who cares about the facts. In particular, the tz database's
-LMT offsets should not be considered meaningful, and should not prompt
-creation of zones merely because two locations differ in LMT or
-transitioned to standard time at different dates.
-
-
------ Time and date functions -----
-
-The tz code contains time and date functions that are upwards
-compatible with those of POSIX.
-
-POSIX has the following properties and limitations.
-
-* In POSIX, time display in a process is controlled by the
- environment variable TZ. Unfortunately, the POSIX TZ string takes
- a form that is hard to describe and is error-prone in practice.
- Also, POSIX TZ strings can't deal with other (for example, Israeli)
- daylight saving time rules, or situations where more than two
- time zone abbreviations are used in an area.
-
- The POSIX TZ string takes the following form:
-
- stdoffset[dst[offset][,date[/time],date[/time]]]
-
- where:
-
- std and dst
- are 3 or more characters specifying the standard
- and daylight saving time (DST) zone names.
- Starting with POSIX.1-2001, std and dst may also be
- in a quoted form like ""; this allows
- "+" and "-" in the names.
- offset
- is of the form '[+-]hh:[mm[:ss]]' and specifies the
- offset west of UT. 'hh' may be a single digit; 0<=hh<=24.
- The default DST offset is one hour ahead of standard time.
- date[/time],date[/time]
- specifies the beginning and end of DST. If this is absent,
- the system supplies its own rules for DST, and these can
- differ from year to year; typically US DST rules are used.
- time
- takes the form 'hh:[mm[:ss]]' and defaults to 02:00.
- This is the same format as the offset, except that a
- leading '+' or '-' is not allowed.
- date
- takes one of the following forms:
- Jn (1<=n<=365)
- origin-1 day number not counting February 29
- n (0<=n<=365)
- origin-0 day number counting February 29 if present
- Mm.n.d (0[Sunday]<=d<=6[Saturday], 1<=n<=5, 1<=m<=12)
- for the dth day of week n of month m of the year,
- where week 1 is the first week in which day d appears,
- and '5' stands for the last week in which day d appears
- (which may be either the 4th or 5th week).
- Typically, this is the only useful form;
- the n and Jn forms are rarely used.
-
- Here is an example POSIX TZ string, for US Pacific time using rules
- appropriate from 1987 through 2006:
-
- TZ='PST8PDT,M4.1.0/02:00,M10.5.0/02:00'
-
- This POSIX TZ string is hard to remember, and mishandles time stamps
- before 1987 and after 2006. With this package you can use this
- instead:
-
- TZ='America/Los_Angeles'
-
-* POSIX does not define the exact meaning of TZ values like "EST5EDT".
- Typically the current US DST rules are used to interpret such values,
- but this means that the US DST rules are compiled into each program
- that does time conversion. This means that when US time conversion
- rules change (as in the United States in 1987), all programs that
- do time conversion must be recompiled to ensure proper results.
-
-* The TZ environment variable is process-global, which makes it hard
- to write efficient, thread-safe applications that need access
- to multiple time zones.
-
-* In POSIX, there's no tamper-proof way for a process to learn the
- system's best idea of local wall clock. (This is important for
- applications that an administrator wants used only at certain times -
- without regard to whether the user has fiddled the "TZ" environment
- variable. While an administrator can "do everything in UTC" to get
- around the problem, doing so is inconvenient and precludes handling
- daylight saving time shifts - as might be required to limit phone
- calls to off-peak hours.)
-
-* POSIX provides no convenient and efficient way to determine the UT
- offset and time zone abbreviation of arbitrary time stamps,
- particularly for time zone settings that do not fit into the
- POSIX model.
-
-* POSIX requires that systems ignore leap seconds.
-
-* The tz code attempts to support all the time_t implementations
- allowed by POSIX. The time_t type represents a nonnegative count of
- seconds since 1970-01-01 00:00:00 UTC, ignoring leap seconds.
- In practice, time_t is usually a signed 64- or 32-bit integer; 32-bit
- signed time_t values stop working after 2038-01-19 03:14:07 UTC, so
- new implementations these days typically use a signed 64-bit integer.
- Unsigned 32-bit integers are used on one or two platforms,
- and 36-bit and 40-bit integers are also used occasionally.
- Although earlier POSIX versions allowed time_t to be a
- floating-point type, this was not supported by any practical
- systems, and POSIX.1-2013 and the tz code both require time_t
- to be an integer type.
-
-These are the extensions that have been made to the POSIX functions:
-
-* The "TZ" environment variable is used in generating the name of a file
- from which time zone information is read (or is interpreted a la
- POSIX); "TZ" is no longer constrained to be a three-letter time zone
- name followed by a number of hours and an optional three-letter
- daylight time zone name. The daylight saving time rules to be used
- for a particular time zone are encoded in the time zone file;
- the format of the file allows U.S., Australian, and other rules to be
- encoded, and allows for situations where more than two time zone
- abbreviations are used.
-
- It was recognized that allowing the "TZ" environment variable to
- take on values such as "America/New_York" might cause "old" programs
- (that expect "TZ" to have a certain form) to operate incorrectly;
- consideration was given to using some other environment variable
- (for example, "TIMEZONE") to hold the string used to generate the
- time zone information file name. In the end, however, it was decided
- to continue using "TZ": it is widely used for time zone purposes;
- separately maintaining both "TZ" and "TIMEZONE" seemed a nuisance;
- and systems where "new" forms of "TZ" might cause problems can simply
- use TZ values such as "EST5EDT" which can be used both by
- "new" programs (a la POSIX) and "old" programs (as zone names and
- offsets).
-
-* The code supports platforms with a UT offset member in struct tm,
- e.g., tm_gmtoff.
-
-* The code supports platforms with a time zone abbreviation member in
- struct tm, e.g., tm_zone.
-
-* Since the "TZ" environment variable can now be used to control time
- conversion, the "daylight" and "timezone" variables are no longer
- needed. (These variables are defined and set by "tzset"; however, their
- values will not be used by "localtime.")
-
-* Functions tzalloc, tzfree, localtime_rz, and mktime_z for
- more-efficient thread-safe applications that need to use
- multiple time zones. The tzalloc and tzfree functions
- allocate and free objects of type timezone_t, and localtime_rz
- and mktime_z are like localtime_r and mktime with an extra
- timezone_t argument. The functions were inspired by NetBSD.
-
-* A function "tzsetwall" has been added to arrange for the system's
- best approximation to local wall clock time to be delivered by
- subsequent calls to "localtime." Source code for portable
- applications that "must" run on local wall clock time should call
- "tzsetwall();" if such code is moved to "old" systems that don't
- provide tzsetwall, you won't be able to generate an executable program.
- (These time zone functions also arrange for local wall clock time to be
- used if tzset is called - directly or indirectly - and there's no "TZ"
- environment variable; portable applications should not, however, rely
- on this behavior since it's not the way SVR2 systems behave.)
-
-* Negative time_t values are supported, on systems where time_t is signed.
-
-* These functions can account for leap seconds, thanks to Bradley White.
-
-Points of interest to folks with other systems:
-
-* Code compatible with this package is already part of many platforms,
- including GNU/Linux, Android, the BSDs, Chromium OS, Cygwin, AIX, iOS,
- BlackBery 10, macOS, Microsoft Windows, OpenVMS, and Solaris.
- On such hosts, the primary use of this package
- is to update obsolete time zone rule tables.
- To do this, you may need to compile the time zone compiler
- 'zic' supplied with this package instead of using the system 'zic',
- since the format of zic's input is occasionally extended,
- and a platform may still be shipping an older zic.
-
-* The UNIX Version 7 "timezone" function is not present in this package;
- it's impossible to reliably map timezone's arguments (a "minutes west
- of GMT" value and a "daylight saving time in effect" flag) to a
- time zone abbreviation, and we refuse to guess.
- Programs that in the past used the timezone function may now examine
- tzname[localtime(&clock)->tm_isdst] to learn the correct time
- zone abbreviation to use. Alternatively, use
- localtime(&clock)->tm_zone if this has been enabled.
-
-* The 4.2BSD gettimeofday function is not used in this package.
- This formerly let users obtain the current UTC offset and DST flag,
- but this functionality was removed in later versions of BSD.
-
-* In SVR2, time conversion fails for near-minimum or near-maximum
- time_t values when doing conversions for places that don't use UT.
- This package takes care to do these conversions correctly.
- A comment in the source code tells how to get compatibly wrong
- results.
-
-The functions that are conditionally compiled if STD_INSPIRED is defined
-should, at this point, be looked on primarily as food for thought. They are
-not in any sense "standard compatible" - some are not, in fact, specified in
-*any* standard. They do, however, represent responses of various authors to
-standardization proposals.
-
-Other time conversion proposals, in particular the one developed by folks at
-Hewlett Packard, offer a wider selection of functions that provide capabilities
-beyond those provided here. The absence of such functions from this package
-is not meant to discourage the development, standardization, or use of such
-functions. Rather, their absence reflects the decision to make this package
-contain valid extensions to POSIX, to ensure its broad acceptability. If
-more powerful time conversion functions can be standardized, so much the
-better.
-
-
------ Interface stability -----
-
-The tz code and data supply the following interfaces:
-
- * A set of zone names as per "Names of time zone rules" above.
-
- * Library functions described in "Time and date functions" above.
-
- * The programs tzselect, zdump, and zic, documented in their man pages.
-
- * The format of zic input files, documented in the zic man page.
-
- * The format of zic output files, documented in the tzfile man page.
-
- * The format of zone table files, documented in zone1970.tab.
-
- * The format of the country code file, documented in iso3166.tab.
-
- * The version number of the code and data, as the first line of
- the text file 'version' in each release.
-
-Interface changes in a release attempt to preserve compatibility with
-recent releases. For example, tz data files typically do not rely on
-recently-added zic features, so that users can run older zic versions
-to process newer data files. The tz-link.htm file describes how
-releases are tagged and distributed.
-
-Interfaces not listed above are less stable. For example, users
-should not rely on particular UT offsets or abbreviations for time
-stamps, as data entries are often based on guesswork and these guesses
-may be corrected or improved.
-
-
------ Calendrical issues -----
-
-Calendrical issues are a bit out of scope for a time zone database,
-but they indicate the sort of problems that we would run into if we
-extended the time zone database further into the past. An excellent
-resource in this area is Nachum Dershowitz and Edward M. Reingold,
-Calendrical Calculations: Third Edition, Cambridge University Press (2008)
-.
-Other information and sources are given below. They sometimes disagree.
-
-
-France
-
-Gregorian calendar adopted 1582-12-20.
-French Revolutionary calendar used 1793-11-24 through 1805-12-31,
-and (in Paris only) 1871-05-06 through 1871-05-23.
-
-
-Russia
-
-From Chris Carrier (1996-12-02):
-On 1929-10-01 the Soviet Union instituted an "Eternal Calendar"
-with 30-day months plus 5 holidays, with a 5-day week.
-On 1931-12-01 it changed to a 6-day week; in 1934 it reverted to the
-Gregorian calendar while retaining the 6-day week; on 1940-06-27 it
-reverted to the 7-day week. With the 6-day week the usual days
-off were the 6th, 12th, 18th, 24th and 30th of the month.
-(Source: Evitiar Zerubavel, _The Seven Day Circle_)
-
-
-Mark Brader reported a similar story in "The Book of Calendars", edited
-by Frank Parise (1982, Facts on File, ISBN 0-8719-6467-8), page 377. But:
-
-From: Petteri Sulonen (via Usenet)
-Date: 14 Jan 1999 00:00:00 GMT
-...
-
-If your source is correct, how come documents between 1929 and 1940 were
-still dated using the conventional, Gregorian calendar?
-
-I can post a scan of a document dated December 1, 1934, signed by
-Yenukidze, the secretary, on behalf of Kalinin, the President of the
-Executive Committee of the Supreme Soviet, if you like.
-
-
-
-Sweden (and Finland)
-
-From: Mark Brader
-Subject: Re: Gregorian reform - a part of locale?
-
-Date: 1996-07-06
-
-In 1700, Denmark made the transition from Julian to Gregorian. Sweden
-decided to *start* a transition in 1700 as well, but rather than have one of
-those unsightly calendar gaps :-), they simply decreed that the next leap
-year after 1696 would be in 1744 - putting the whole country on a calendar
-different from both Julian and Gregorian for a period of 40 years.
-
-However, in 1704 something went wrong and the plan was not carried through;
-they did, after all, have a leap year that year. And one in 1708. In 1712
-they gave it up and went back to Julian, putting 30 days in February that
-year!...
-
-Then in 1753, Sweden made the transition to Gregorian in the usual manner,
-getting there only 13 years behind the original schedule.
-
-(A previous posting of this story was challenged, and Swedish readers
-produced the following references to support it: "Tideräkning och historia"
-by Natanael Beckman (1924) and "Tid, en bok om tideräkning och
-kalenderväsen" by Lars-Olof Lodén (1968).
-
-
-Grotefend's data
-
-From: "Michael Palmer" [with one obvious typo fixed]
-Subject: Re: Gregorian Calendar (was Re: Another FHC related question
-Newsgroups: soc.genealogy.german
-Date: Tue, 9 Feb 1999 02:32:48 -800
-...
-
-The following is a(n incomplete) listing, arranged chronologically, of
-European states, with the date they converted from the Julian to the
-Gregorian calendar:
-
-04/15 Oct 1582 - Italy (with exceptions), Spain, Portugal, Poland (Roman
- Catholics and Danzig only)
-09/20 Dec 1582 - France, Lorraine
-
-21 Dec 1582/
- 01 Jan 1583 - Holland, Brabant, Flanders, Hennegau
-10/21 Feb 1583 - bishopric of Liege (Lüttich)
-13/24 Feb 1583 - bishopric of Augsburg
-04/15 Oct 1583 - electorate of Trier
-05/16 Oct 1583 - Bavaria, bishoprics of Freising, Eichstedt, Regensburg,
- Salzburg, Brixen
-13/24 Oct 1583 - Austrian Oberelsaß and Breisgau
-20/31 Oct 1583 - bishopric of Basel
-02/13 Nov 1583 - duchy of Jülich-Berg
-02/13 Nov 1583 - electorate and city of Köln
-04/15 Nov 1583 - bishopric of Würzburg
-11/22 Nov 1583 - electorate of Mainz
-16/27 Nov 1583 - bishopric of Strassburg and the margraviate of Baden
-17/28 Nov 1583 - bishopric of Münster and duchy of Cleve
-14/25 Dec 1583 - Steiermark
-
-06/17 Jan 1584 - Austria and Bohemia
-11/22 Jan 1584 - Lucerne, Uri, Schwyz, Zug, Freiburg, Solothurn
-12/23 Jan 1584 - Silesia and the Lausitz
-22 Jan/
- 02 Feb 1584 - Hungary (legally on 21 Oct 1587)
- Jun 1584 - Unterwalden
-01/12 Jul 1584 - duchy of Westfalen
-
-16/27 Jun 1585 - bishopric of Paderborn
-
-14/25 Dec 1590 - Transylvania
-
-22 Aug/
- 02 Sep 1612 - duchy of Prussia
-
-13/24 Dec 1614 - Pfalz-Neuburg
-
- 1617 - duchy of Kurland (reverted to the Julian calendar in
- 1796)
-
- 1624 - bishopric of Osnabrück
-
- 1630 - bishopric of Minden
-
-15/26 Mar 1631 - bishopric of Hildesheim
-
- 1655 - Kanton Wallis
-
-05/16 Feb 1682 - city of Strassburg
-
-18 Feb/
- 01 Mar 1700 - Protestant Germany (including Swedish possessions in
- Germany), Denmark, Norway
-30 Jun/
- 12 Jul 1700 - Gelderland, Zutphen
-10 Nov/
- 12 Dec 1700 - Utrecht, Overijssel
-
-31 Dec 1700/
- 12 Jan 1701 - Friesland, Groningen, Zürich, Bern, Basel, Geneva,
- Turgau, and Schaffhausen
-
- 1724 - Glarus, Appenzell, and the city of St. Gallen
-
-01 Jan 1750 - Pisa and Florence
-
-02/14 Sep 1752 - Great Britain
-
-17 Feb/
- 01 Mar 1753 - Sweden
-
-1760-1812 - Graubünden
-
-The Russian empire (including Finland and the Baltic states) did not
-convert to the Gregorian calendar until the Soviet revolution of 1917.
-
-Source: H. Grotefend, _Taschenbuch der Zeitrechnung des deutschen
-Mittelalters und der Neuzeit_, herausgegeben von Dr. O. Grotefend
-(Hannover: Hahnsche Buchhandlung, 1941), pp. 26-28.
-
-
------ Time and time zones on Mars -----
-
-Some people's work schedules use Mars time. Jet Propulsion Laboratory
-(JPL) coordinators have kept Mars time on and off at least since 1997
-for the Mars Pathfinder mission. Some of their family members have
-also adapted to Mars time. Dozens of special Mars watches were built
-for JPL workers who kept Mars time during the Mars Exploration
-Rovers mission (2004). These timepieces look like normal Seikos and
-Citizens but use Mars seconds rather than terrestrial seconds.
-
-A Mars solar day is called a "sol" and has a mean period equal to
-about 24 hours 39 minutes 35.244 seconds in terrestrial time. It is
-divided into a conventional 24-hour clock, so each Mars second equals
-about 1.02749125 terrestrial seconds.
-
-The prime meridian of Mars goes through the center of the crater
-Airy-0, named in honor of the British astronomer who built the
-Greenwich telescope that defines Earth's prime meridian. Mean solar
-time on the Mars prime meridian is called Mars Coordinated Time (MTC).
-
-Each landed mission on Mars has adopted a different reference for
-solar time keeping, so there is no real standard for Mars time zones.
-For example, the Mars Exploration Rover project (2004) defined two
-time zones "Local Solar Time A" and "Local Solar Time B" for its two
-missions, each zone designed so that its time equals local true solar
-time at approximately the middle of the nominal mission. Such a "time
-zone" is not particularly suited for any application other than the
-mission itself.
-
-Many calendars have been proposed for Mars, but none have achieved
-wide acceptance. Astronomers often use Mars Sol Date (MSD) which is a
-sequential count of Mars solar days elapsed since about 1873-12-29
-12:00 GMT.
-
-The tz database does not currently support Mars time, but it is
-documented here in the hopes that support will be added eventually.
-
-Sources:
-
-Michael Allison and Robert Schmunk,
-"Technical Notes on Mars Solar Time as Adopted by the Mars24 Sunclock"
- (2012-08-08).
-
-Jia-Rui Chong, "Workdays Fit for a Martian", Los Angeles Times
-
-(2004-01-14), pp A1, A20-A21.
-
-Tom Chmielewski, "Jet Lag Is Worse on Mars", The Atlantic (2015-02-26)
-
-
------
-
-This file is in the public domain, so clarified as of 2009-05-17 by
-Arthur David Olson.
-
------
-Local Variables:
-coding: utf-8
-End: