Abstract:Introduction to the knowledge and use of time zones in GausSDB (DWS).
This article was shared from Huawei Cloud Community “Time Zones Everyone Knows, There Are Some Secrets Behind They Are” by LEAPDB.
background
Like other industry standards, the process of standardizing time zones is a complex and lengthy process. GAUSSDB (DWS) is a high-performance analytical database product for global users, and its support for time zones is in line with industry standards and specifications. Here is an introduction to GausSDB (DWS) from the concept of time zones, the use and rationale of GausSDB (DWS) time zones, and some common questions.
I hope it will be helpful for you to understand the concept of GAUSSDB (DWS) and time zone.
Concept paper
In the past, when countries all over the world were agricultural, people determined the time by observing the position of the sun each day, which made the time different at different longitudes. At that time, people traveled mainly on foot and by horse, and time inconsistencies in different places were less of a problem. But in the 19th century, with the invention of the train, people traveled far longer in a day, and there was an urgent need for a universal way to unify time in different places. August 12, 1853. Fourteen people are killed when two trains collide head-on in the eastern state of Rhode Island. The cause of the accident seems hard to believe today – the engineers’ watches were two minutes apart.
- In 1863, the concept of time zones was first used. Time zones solve this problem in part by setting the standard time for an area.
- In the 1870s, Canadian railroad engineer John Fleming first proposed a unified time zone for the world.
- On November 18, 1883, the United States Railroad officially adopted five time zones.
- It was formally adopted at the Meridian International Conference in Washington in 1884 and became known as the Universal Standard Time System. As a result, the birth of the World Standard Time Zone has been a slow development, as have other global standards.
1. Interpretation of nouns
Time zone A time zone is an area of the earth that uses the same time definition. Previously, people determined time by looking at the position of the sun (hour Angle), which made time different in places with different longitude (local time). In 1863, the concept of time zones was first used. Time zones solve this problem in part by setting the standard time for an area. Every country in the world is located in different parts of the earth, so different countries, especially countries with a large east-west span, are bound to have different sunrise and sunset times. These deviations are known as jet lag.
Greenwich Mean Time (GMT) refers to the standard Time of the Royal Greenwich Observatory, located in the suburbs of London, United Kingdom, because the prime meridian is defined as the longitude that passes there. Because the Earth moves at an uneven speed in its elliptical orbit, its daily rotation is somewhat irregular, and it is slowly slowing down. So Greenwich time is no longer used as standard time.
UTC (Coordinated Universal Time) is an actuarial calculation combining mean solar Time (GMT), a new Time scale adjusted for Earth’s axis motion, and international atomic Time in seconds. UTC is more accurate than GMT. For current watches, there is no difference in function and accuracy between GMT and UTC.
DST (Daylight Saving Time) is also known as Daylight Saving Time (Daylight Saving Time). In Britain, it is called Summer Time. It is a system of setting local time artificially for the purpose of saving energy. The uniform time used during this system is called “daylight saving time”. The summer that is earlier in dawn commonly artificially adjusts time fast one hour, can make the person gets up early sleep early, reduce illumination quantity, in order to make full use of illumination resource, economize illuminating electricity thereby. Countries that adopt daylight saving time have different regulations.
Time zone representation If the time is expressed in Coordinated Universal Time (UTC), a “Z” is added directly after the time (without space). “Z” is the symbol for time zone 0 in Coordinated Universal Time. Therefore, “09:30 UTC” would be written as “09:30Z” or “0930Z”. “14:45:15 UTC” is “14:45:15Z” or “144515Z”. UTC is also known as Zulu Time because of the “Zulu” in the NATO phonetic alphabet for “Z”.
UTC Offset The UTC Offset is the date and time difference in Coordinated Universal Time (UTC) and at a particular location, in hours and minutes. It is usually shown in ±[hh]:[mm], ±hh, or ±[hh] format. So, if the time being described is one hour earlier than UTC (such as winter time in Berlin), the UTC offset will be “+01:00”, “+0100”, or simply displayed as “+01”.
Time adjustment by country
- Morocco changed daylight saving time from June 1 to May 2 and from August 21 to August 8 in 2010
- Tunisia abolished Daylight Saving Time in 2010
- Macquarie Island, located midway between Australia and Antarctica, decided not to join the rest of Australia in adopting daylight saving time from April 4, 2010, creating a new time zone, Antartica /Macquarie, or MIST
- North Korea – Since May 5, 2018, the time zone has been changed from GMT+8:30 to GMT+9:00, so Pyongyang’s standard time has been moved forward 30 minutes from 00:00:00 on Saturday, May 5, 2018 to 00:30:00. When GMT is 0:00 a.m., Pyongyang time is 9:00 a.m., the same time zone as South Korea and Japan.
- North Korea – Since 15 August 2015, it has abandoned GMT+9 and “reverted” to the Korean Empire’s GMT+8:30 standard time, which is 30 minutes slower than the original time. It is the only country in the world to use this time zone. When GMT is 0:00 a.m., Pyongyang time is 8:30 a.m.
- Chile – On January 28, 2015, Chile adopted a new official standard time. They merged standard time and daylight saving time into one, making daylight saving time permanent. The new official time will be GMT-3 in mainland Chile and GMT-5 in Easter Island.
- Russia – Starting in the wee hours of the last Sunday of October 2014 (26 October 2014), winter time will be adopted permanently and the whole country will set back one hour. So Moscow time will be changed from GMT+4 to GMT+3.
As you can see, both the time zone and daylight saving time will often change.
2 Common time format
Main reference is POSIX 1003.1 Section 8.3. The TZ environment variable in the operating system represents time zone information and is mainly used for CTime, LocalTime, MkTime, and so on. TZ time zone names come in two forms: time zone name format and POSIX time zone format.
2.1 Time zone name format
This form starts with a colon, and subsequent character processing is implementation-specific. On Linux, it means reading time zone information from a file, such as TZ=”:Pacific/Auckland”.
2.2 POSIX time zone format
Std offsetdst[offset, enddate[/time]] [offset, enddate[/time]]]
DST [offset][, startDate [/time], endDate [/time]]]
The meaning of each field is as follows:
- STD && DST stands for Standard Time Zone and Daylight Saving Time Zone. STD is required and DST is optional (with a DST field, it supports Daylight Saving Time). These two fields have two formats:
- A. A reference symbol <>, the string in the reference symbol can be letters, numbers, +, -, parsing does not contain the reference symbol <>;
- B. The other has no reference symbol <>, and the string can only be an alphabet.
Field length is greater than or equal to 3, less than or equal to TZNAME_MAX (Linux is 6), if the string length is not specified, parsing rules are not defined (Linux is not recognized).
- Offset represents how much local time is added to get UTC time.
The format is hh[:mm[:ss]], 0<=hh<= 24,0 <= m&&ss<=59. HH is required and can be 1 bit, MM and SS are optional.
- If it is preceded by a plus sign, it means west of the prime meridian. Indicates how much time is added to this time to get the UTC time. The plus sign is also not carried.
- If you put a minus sign in front of it, it means east of the prime meridian. Indicates how much time is subtracted from this time to obtain the UTC time.
Offset after STD is required. Offset after DST is optional. If not, it defaults to one hour ahead of standard time.
- Rule said when it began to daylight saving time, when the end of the daylight saving time, agreement did not mention how to deal with the situation there is no rule, from the point of Linux system, there is no default rule by M3.2.0/02:00:00, M11.1.0/02:00:00 processing.
The format is date[/time],date[/time]. Date has three forms:
A. Jn, 1 <= n <= 365, not including February 29 in leap years; B. N, 0 <= n <= 365, including February 29 in leap years; C. mm. n.d, m is the month (1 <= m <= 12), n is the week of the month (1 <= n <= 5), 5 is the last one, and d is the day of the week (0 <= d <= 6, starting on Sunday).
- The format of time is the same as offset, except that there are no + and -. If there is no time field, the default is 02:00:00.
For example: “UTC – 8:00:00 DST – 09:00:00 M3.2.0/02:00:00, M11.1.0/02:00:00”, said the local time to UTC east 8 hours, support daylight saving time and daylight saving time for UTC minus nine hours (and) an hour earlier, Daylight saving time starts at 2 am on the 0th day of the 2nd week of March and ends at 2 am on the 0th day of the 1st week of November. CST6CDT M3.2.0/2:00:00, M11.1.0/2:00:00
The POSIX time zone format has not been widely adopted because it does not represent times that do not use the Gregorian calendar (such as Greece).
Universal time zone database
Local time zones and daylight saving time rules are administered independently by their respective governments, which often change them with limited notice. And their historical data and future plans are only intermittently recorded. The Universal Time Zone Database attempts to organize and collate relevant data in this field.
A time zone database, commonly known as TZ, TZData or ZoneInfo, is a collection of code and data that represents the historical local time of a number of representative locations around the world. It is updated irregularly according to changes in time zone boundaries and daylight saving time rules by various regimes. Each entry in the database represents time zone information for the widely accepted civil clock since 1970. The database is referenced by many projects, such as: the GNU C Library (used in GNU/Linux), Android, FreeBSD, NetBSD, OpenBSD, Chromium OS, Cygwin, MariaDB, MINIX, MySQL, WebOS, AIX, BlackBerry 10, iOS, MacOS, Microsoft Windows, OpenVMS, Oracle Database, and Oracle Solaris. GAUSSDB, like other widely used software products, uses common time zone data maintained by IANA.
The database was created by David Olson and edited and maintained by Paul Eggert. It is also known in some places as the Olson database. Its notable feature is a common naming convention for time zones designed by Paul Eggert. Each time zone is given a unique name, such as “America/New_York”, in a “region/location” format. Spaces in English place names are replaced by an underscore “_” and the conjunction “-” is used only when the English place name itself is included. There are two common time zone databases called Olson time zone databases or IANA time zone databases.
Olson’s numbers changed, partly because Ad Olson was retiring and partly because of a (now withdrawn) lawsuit against the maintainers for copyright infringement. On 14 October 2011, the International Corporation for Assigned Names and Names (IANA) took over maintenance of the time zone database. It is regularly updated to reflect changes by political entities to time zone boundaries, UTC differentials, and daylight saving time rules. Updates to the TZ are managed according to the BCP 175 process. Countries often change their time zone rules, and IANA releases the latest time zone data and parsing source library every year.
In fact, how time zones are defined and managed is a matter of controversy, and there is no definitive database of time zones. The universal time zone database maintained by IANA became widely used with the adoption of the GNU C Library and BSD because each record identifies a clear source of information, has historical information and can predict the future time. In fact there are other time zone database, for example: Microsoft’s time zone database, HP – UX time zone database, world time server (https://www.worldtimeserver.com/) and the international air transport association “standard schedule information handbook”, etc.
Practical article
1 Use of the GausSDB (DWS) time zone
The system table PG_TIMEZONE_NAMES records the timezone names.
testdb=# select * from pg_timezone_names where utc_offset='08:00:00'; name | abbrev | utc_offset | is_dst --------------------+--------+------------+-------- Asia/Kuala_Lumpur | +08 | 08:00:00 | f Asia/Brunei | +08 | 08:00:00 | f Asia/Makassar | WITA | 08:00:00 | f Asia/Harbin | CST | 08:00:00 | f Asia/Ujung_Pandang | WITA | 08:00:00 | f Asia/Chungking | CST | 08:00:00 | f Asia/Kuching | +08 | 08:00:00 | f Asia/Taipei | CST | 08:00:00 | f Asia/Macau | CST | 08:00:00 | f Asia/Macao | CST | 08:00:00 | f Asia/Manila | PST | 08:00:00 | f Asia/Chongqing | CST | 08:00:00 | f Asia/Shanghai | CST | 08:00:00 | f Asia/Choibalsan | +08 | 08:00:00 | f Asia/Ulaanbaatar | +08 | 08:00:00 | f Asia/Irkutsk | +08 | 08:00:00 | f Asia/Ulan_Bator | +08 | 08:00:00 | f Asia/Hong_Kong | HKT | 08:00:00 | f Asia/Singapore | +08 | 08:00:00 | f Australia/West | AWST | 08:00:00 | f Australia/Perth | AWST | 08:00:00 | f ROC | CST | 08:00:00 | f Etc/GMT-8 | +08 | 08:00:00 | f PRC | CST | 08:00:00 | f Singapore | +08 | 08:00:00 | f Antarctica/Casey | +08 | 08:00:00 | f Hongkong | HKT | 08:00:00 | f (27 rows)The system table PG_TIMEZONE_ABBREVS records the timezone abbreviations
testdb=# select * from pg_timezone_abbrevs where utc_offset='08:00:00'; abbrev | utc_offset | is_dst --------+------------+-------- AWST | 08:00:00 | f BNT | 08:00:00 | f BORT | 08:00:00 | f CCT | 08:00:00 | f HKT | 08:00:00 | f IRKST | 08:00:00 | f IRKT | 08:00:00 | f MYT | 08:00:00 | f PHT | 08:00:00 | f SGT | 08:00:00 | f ULAT | 08:00:00 | f WADT | 08:00:00 | t (12 rows)By setting the session environment variable TIMEZONE, you can set the timezone of database data entering and querying. Why session level? What if the user doesn’t set a different time zone, or if the user forgets the previous time zone?
A: After the time data is stored in the database, the database management software will convert the time into UTC 0 time zone. When the user queries, the time will be converted into the corresponding time according to the time zone set by the user. Therefore, the time zone set by the user does not affect the data storage, nor does it matter when the data is migrated.
2 How to set the default time zone when GaussDB(DWS) is initialized
If the time zone is not specified in the configuration file, the current operating system time zone is obtained from the current operating system environment variable TZ, and the time zone is a supported time zone in the database, then the operating system time zone is used directly. Otherwise, some dates are constructed based on the current time of the operating system to determine which time zone matches the operating system best.
Evaluation Method:
1) Collect some timestamps 100 years from now
First, detect the January and July of the current year, which can quickly eliminate a large number of non-conforming time zones. Second, probing every week for 100 years from July of the current year effectively excludes time zones that do not correspond to daylight saving time.
tnow = time(NULL); // Gets the number of seconds since 1970-01-01 00:00:00 UTC tm_val = localtime(&tnow); ThisYear = tm_val->tm_year + 1900; thisYear = tm_val->tm_year + 1900; thisYear = tm_val->tm_year + 1900; //tm_year is the number of years since 1900, so add 1900 time_needto_test = 0; Thisyear (thisyear, 1, 15); thisyear (thisyear, 1, 15); t -= (t % T_WEEK); test_times[time_needto_test++] = t; 00:00:00 t = MakeTime(thisyear, 7, 15); t -= (t % T_WEEK); test_times[time_needto_test++] = t; While (tt.n_test_times < 52 * 100) {t -= T_WEEK; test_times[time_needto_test++] = t; } // A total of 5202 probe times were constructed2) Judge the matching degree between the internal time zone of each database and the time zone of the operating system
If a timestamp is converted to the operating system time zone at the same time as it was converted to the internal time zone of the database under test, add a point. Encountering a mismatch ends the current time zone match.
First, determine the match between the time zone in “/etc/localtime” and the previous test time, and return success if the match is complete.
Otherwise, determine the degree to which each timezone file under the database installation directory timezone matches the previous test time to get the timezone with the highest degree of match.
Bestscore = 0; For (for each timezone file) {score = score_timezone(tzdirsub, tt); If (score > bestScore) {// BestScore = score; bestzonename = tzdirsub; } else if (score == bestScore) {// If the current time zone is equal to the current maximum match, select the length shorter, If more of the time zone (alphabetical order (strlen (tzdirsub) < strlen (bestzonename) | | (strlen (tzdirsub) = = strlen (bestzonename) && STRCMP (tzdirsub, bestzonename) < 0)) strlcpy(bestzonename, tzdirsub, TZ_STRLEN_MAX + 1); }}3) If all database internal time zones match and the best score is still 0, then you need to construct a POSIX-style time zone consistent with the operating system time zone, for example: “PSD8PDT”
Cold knowledge article
What are the time zones in China and how are they set?
Before 1912, there was no standard time for all parts of China. In feudal times, the country’s standard calendar was promulgated by the imperial court, but the traditional Chinese calendar relied on the movement of the sun and the moon, and was based on actual astronomical observations. Therefore, the duration of the calendar was based on the longitude and latitude of the location of the imperial court (to be precise, the observation point of Qin Tian Jian).
In 1912, the Republic of China was established, and the first time zone division was established and officially promulgated. China was divided into five time zones, which were officially promulgated in 1939.
1: Kunlun Time Zone (GMT+5:30)
2: New Tibetan Time Zone (GMT+6)
3: Longshu Time Zone (GMT+7)
4: Central Plains Standard Time Zone (GMT+8)
5: White Time Zone (GMT+8:30)
The details are as follows:
Asia/Harbin is also called Changbai time zone, which mainly represents the time of Heilongjiang (excluding Mohe) and Jilin regions
# Zone NAME GMTOFF RULES FORMAT [UNTIL]
# Changbai Time ("Long-white Time", Long-white = Heilongjiang area)
# Heilongjiang (except Mohe county), Jilin
Zone Asia/Harbin 8:26:44 - LMT 1928 # or Haerbin
8:30 - CHAT 1932 Mar # Changbai Time
8:00 - CST 1940
9:00 - CHAT 1966 May
8:30 - CHAT 1980 May
8:00 PRC C%sTAsia/Shanghai is also called the Central Plains Standard Time Zone
# Zhongyuan Time ("Central plain Time")
# most of China
# Milne gives 8:05:56.7; round to nearest.
Zone Asia/Shanghai 8:05:57 - LMT 1928
8:00 Shang C%sT 1949
8:00 PRC C%sTAsia/Chongqing, also called hazy shu time zone, mainly represents guangxi, guizhou, hainan, ningxia, sichuan, shaanxi, yunnan, gansu, western inner Mongol, western qinghai, guangdong deqing, enping, kaiping, luoding, Taishan, xinxing, yangchun, yangjiang, yunan, yunfu, for the seventh district of the east.
# Long-shu Time (probably due to Long and Shu being two names of that area)
# Guangxi, Guizhou, Hainan, Ningxia, Sichuan, Shaanxi, and Yunnan;
# most of Gansu; west Inner Mongolia; west Qinghai; and the Guangdong
# counties Deqing, Enping, Kaiping, Luoding, Taishan, Xinxing,
# Yangchun, Yangjiang, Yu'nan, and Yunfu.
Zone Asia/Chongqing 7:06:20 - LMT 1928 # or Chungking
7:00 - LONT 1980 May # Long-shu Time
8:00 PRC C%sTAsia/Urumqi is also called the new Tibetan time zone, which mainly represents Akesha Autonomous County, Anxi County, Dunhuang, Subei County, Lianjiang County, Zhanjiang City and so on.
# Xin-zang Time ("Xinjiang-Tibet Time")
# The Gansu counties Aksay, Anxi, Dunhuang, Subei; west Qinghai;
# the Guangdong counties Xuwen, Haikang, Suixi, Lianjiang,
# Zhanjiang, Wuchuan, Huazhou, Gaozhou, Maoming, Dianbai, and Xinyi;
# east Tibet, including Lhasa, Chamdo, Shigaise, Jimsar, Shawan and Hutubi;
# east Xinjiang, including Urumqi, Turpan, Karamay, Korla, Minfeng, Jinghe,
# Wusu, Qiemo, Xinyan, Wulanwusu, Jinghe, Yumin, Tacheng, Tuoli, Emin,
# Shihezi, Changji, Yanqi, Heshuo, Tuokexun, Tulufan, Shanshan, Hami,
# Fukang, Kuitun, Kumukuli, Miquan, Qitai, and Turfan.
Zone Asia/Urumqi 5:50:20 - LMT 1928 # or Urumchi
6:00 - URUT 1980 May # Urumqi Time
8:00 PRC C%sTAsia/Kashgar is also called Kunlun time zone, mainly representing western Tibet (Pulan County, Aheqi County, Shufu County, Shule County) and western Xinjiang (Aksu, Atushi, Yining, Hotan, Cele, Lopu, Nilek, Zhao Su, Tex, Gongtaru, Qapqal, Huocheng, Bole, Pishan, etc.)
Zone Asia/Kashgar 5:03:56 - LMT 1928 # or Kashi or Kaxgar
5:30 - KAST 1940 # Kashgar Time
5:00 - KAST 1980 May
8:00 PRC C%sTPRC points to the Central Plains Standard Time Zone
After the founding of the People’s Republic of China in 1949, China abolished the Central Plains Standard Time Zone, Kunlun Time Zone, Changbai Time Zone, Longshu Time Zone and Tibet Time Zone established by the former Nationalist Government in 1939, and adopted UTC+8 throughout the country, which was named Beijing Time. After 1950, all parts of the country, except Tibet and Xinjiang, used Beijing time. At that time, the local people’s congress of Xinjiang set Urumqi time (UTC+6) for the convenience of the people. For example, 8:00 in Beijing time and 6:00 in Urumqi time were set. The new time zone adjustments are as follows:
1) Asia/Harbin, Asia/Chongqing, Asia/Shanghai time zone names remain, definitions all refer to the newly defined Asia/Shanghai time zone. Unified use throughout the country.
The Central Plains Standard Time Zone has been renamed to Beijing Time Zone. Offset has been adjusted
# Zone NAME STDOFF RULES FORMAT [UNTIL]
# Beijing time, used throughout China; represented by Shanghai.
Zone Asia/Shanghai 8:05:43 - LMT 1901
8:00 Shang C%sT 1949 May 28
8:00 PRC C%sT2) ASIA/KASHGAR (Kunlun Time Zone), ASIA/URUMQI (New Tibetan Time Zone) time zone names remain, definitions all point to the newly defined ASIA/URUMQI time zone. Both time zone definitions are used locally.
The new Tibetan time zone has been changed to Xinjiang time zone offset
# Xinjiang time, used by many in western China; 20 represented by Urumqi/Urumchi # / Wulumuqi. (Please use Asia/Shanghai if you prefer Beijing time. 5:50:20 - LMT 1928 6:00 - +06The time zone being merged
L ASIA/URUQI ASIA/KASHGAR Kunlun time zone is merged into new Tibetan time zone L ASIA /Shanghai ASIA /Harbin Changbai time zone is merged into central China standard time zone L ASIA /Shanghai ASIA/CHONGQING The new alias of the OZ is Chungking, which is also in line with the standard time zone L Asia/Shanghai PRCWhy is there no Beijing time zone only Beijing time?
Due to a variety of political reasons where the country is located, the name of the country and the country to which the region belongs can change from time to time, which makes time zone management a lot of trouble. For example, the landlocked Kingdom of Swaziland in the southeast of Africa announced in April 2018 that it would change its name to Eswatini. On July 1, 1997, with which we are absolutely familiar, Hong Kong returned from a British colony to the embrace of our great motherland. The country of ownership changed. As a result, IANA’s strategy is to remain neutral to political changes, time zones are generally not tied to countries, and each country or national capital is not required to have a time zone name.
For the convenience of domestic users, GausSDB (DWS) internally helps users to define the Asia/Beijing time zone according to the syntax rules defined by IANA, which is consistent with the definition of PRC time zone.
Are time zone definitions fixed?
How time zones are defined and managed is a matter of debate, and there is no definitive database of time zones. A change in time zone information for a country or territory is a separate matter and there is no obligation to notify IANA. The authority of the IANA time zone database mainly depends on the knowledge of the time zone database maintainers of the relevant countries or regions.
As a result, the IANA time zone definition, which records the sources of time zone information collected by the time zone database maintainer, is sometimes not very objective. The following is the IANA reference for time zone information in our country.
From Guy Harris: From Bob Devine (1988-01-28): See TIME mag, 1986-02-17 p.52. From U. S. Naval Observatory (1989-01-19): From Anthony Fok (2001-12-20): from some Taiwan websites From Paul Eggert (2006-03-22): Devine's note about Time magazine From Jesper Norgaard Welen (2006-07-14): http://www.astro.com/atlas From Paul Eggert (2008-02-11): I just now checked Google News for western news sources From David Cochrane (2014-03-26): https://content.time.com/time/magazine/article/0, 9171960, 684, 00. HTML From Luther Ma (2014-04-22) : Guo's report regarding Xinjiang From Paul Eggert (2014-06-30): http://www.sinkiang.gov.cn/service/ourworking (2014-04-22). From Paul Eggert (2017-01-05): Guo Qing-sheng (National Time-Service Center, CAS, Xi'an 710600, China) (Zhongguo Ke Ji Shi Liao, Science and Technology History in China).2003; 24(1):5-9. http://oversea.cnki.net/kcms/detail/detail.aspx?filename=ZGKS200301000&dbname=CJFD2003 Guo Qing-sheng (Shaanxi Astronomical Observatory, CAS, Xi'an 710600, China) An AP article "Shanghai Internat'l Area Little Changed" From P Chan (2018-05-07): 1986-04-12 http://www.zj.gov.cn/attach/zfgb/198608.pdf p.21-22 1987-02-15 http://www.gov.cn/gongbao/shuju/1987/gwyb198703.pdf p.114 1987-09-09 http://www.gov.cn/gongbao/shuju/1987/gwyb198721.pdf p.709 1992-03-03 http://www.gov.cn/gongbao/shuju/1992/gwyb199205.pdf p.152 http://data.people.com.cn/pic/101p/1988/04/1988041201.jpgIt can be seen that before 2014, IANA collected China time zone information mostly from news and magazines in the West and websites in Taiwan. The information collected after 2014 comes from China’s Xi ‘an Time Management Center, national portals, etc.
In addition, because time zone information changes frequently in many countries, the time zone data in the IANA Universal Time Zone Database is constantly updated. As a universal database product for the world, GausSDB (DWS) also synchronizes the latest time zone information from IANA every time a new release is released, ensuring that users’ software products remain up-to-date with the time zone information.
4. Why do we pay so little attention to time zones?
Since the abolition of daylight saving time in 1992, our time zone information has never changed, which brings great convenience to our production and life. Domestic users no longer need to worry about time zone issues.
conclusion
In summary, GausSDB (DWS), as a high-performance analytical database product for global users, supports time zones in line with industry standards and specifications. The time zone of GausSDB (DWS) is easy to use, and the choice of default time zone is scientific and reasonable.
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