Abstract:This article mainly introduces the origin, development, standardization of daylight saving time and how to query the rules of daylight saving time in any time zone in GausSDB.

This article is shared from Huawei Cloud Community “How DWS and” Daylight Saving Time “Happy Play!” , by LeapDB.

1. Background

To understand more about Daylight Saving Time, let’s take a look at one of the more puzzling news stories:

Xinhuanet Moscow, July 9 (reporter Cao Yan) Russia’s national time zone will be delayed by one hour from October 26, according to a bill passed by the Federation Council (upper house of parliament) on Monday. In the capital, Moscow, for example, is currently four hours ahead of GMT, and after October 26, Moscow will be three hours ahead of GMT.

The bill had already been passed by the Duma, the lower house of parliament, and the president is expected to sign it soon. This is the latest change to Russia’s daylight saving time system since it became permanent in 2011. Russia is a vast country that spans many time zones and has a constant social debate about how to use “reasonable time”. Not everyone is happy with the timing changes.

Due to energy-saving considerations, the former Soviet Union and Russia have used 30 years of daylight saving time. Daylight saving time, also known as daylight saving time, refers to the practice of moving the time forward one hour in the early spring and summer to make better use of sunlight. In many high latitudes, the sun rises significantly earlier in spring and summer than in winter. Daylight saving time allows people to get up early and go to bed earlier, reducing energy consumption for lighting.

Russia had daylight saving time from 1981 to 2011. Clocks are put forward one hour each year on the last Sunday of March; Clocks are set back one hour every year on the last Sunday of October. In the capital Moscow, for example, daylight saving time is four hours ahead of GMT and non-daylight saving time is three hours ahead of GMT.

However, the pros and cons of daylight saving time have been debated. Whether or not daylight saving time saves energy consumption in modern societies is an open question. In addition, medical experts are divided on how much the twice-yearly shift affects the body clock.

Russia stopped using the WST switch in 2011. The president at the time ordered in 2011 that clocks would no longer be set back one hour after the end of daylight saving time that year, and daylight saving time would be permanently used, meaning that Russia’s national time zone would move forward by one hour and Moscow time would be four hours ahead of GMT all year round. The president explained that changing the time frequently disrupted the body’s biological cycle, making people stressed and vulnerable to illness.

For the vast country of Russia, permanent use of daylight saving time can allow residents in different areas to get more sunlight. However, in most regions of Russia, the latitude is high, and the dawn is relatively late in winter. The use of daylight saving time still forces people to get up and go to work in the dark, which makes life difficult.

More than two years into making daylight saving time permanent, there are fewer and fewer supporters. In 2011, when daylight saving time ended, 63 percent of respondents in a poll by the independent Levada Center in Russia supported permanent daylight saving time. But in an October poll by the same research group, the number of respondents in favor of such a move dropped to 41 percent.

Since 2012, a number of legislators have submitted a motion to change the time system. After several delays for various reasons, the State Duma finally began formal discussion in June on a bill to change the time system and make permanent the use of “winter time” instead of daylight saving time. But that doesn’t please everyone. An earlier poll showed that about a third of respondents supported daylight saving time and about a third supported “winter time,” while another third said they didn’t care.

Visible, daylight saving time is an argument ceaseless affair all the time, want to use daylight saving time after all, we still need to look closely from its cause and social development degree.

2. What is Daylight Saving Time, its creation, causes and advantages and disadvantages

Daylight Saving Time (DST) is also known as Daylight Saving Time (Daylight Saving Time). The Time used during this system is called Daylight Saving Time (DST). The summer that is early in the morning commonly artificially adjusts time fast one hour, can make the person gets up early to sleep early, reduce illumination quantity, in order to make full use of illumination resource, save illumination to use electricity thereby. Countries that adopt daylight saving time have different regulations. Nearly 110 countries around the world observe daylight saving time every year.

The process by which daylight saving time came into being and was gradually adopted in many countries:

  1. Franklin, an outstanding American statesman and diplomat (the figure on the $100 bill), was used to the early to bed and early to rise life of rural aristocrats in the United States when he served as the American ambassador to France. When he took a walk in the morning, he saw the French get up at 10 o ‘clock and had a night life until late at night.

In this way, he has little time to communicate and work with French people, which he thinks is a waste of time. So in 1784 he wrote a letter to the editor of the Paris Journal, saying that the habits of the French were a waste of good sunshine, advising them to go to bed early and rise early, and that they would save 64 million pounds of candles a year.

  1. In 1907, British architect William Willett (William Willett) formally proposed the idea of daylight saving time to the British Parliament, mainly in order to save energy and provide more time to train soldiers, but the Parliament did not adopt after debate.
  2. In 1916, Germany, a country that advocates conservation and pays attention to environmental protection, took the lead in trying this project nationwide. As a result, it could save 15% of coal and electricity resources every day.
  3. Fearing that Germany would benefit more from it, Britain followed suit, saving about 15% on gas and electricity.
  4. After both Britain and Germany adopted daylight saving time, France soon followed suit.

6 In 1917, daylight saving time was first observed in Russia.

  1. In 1918, daylight saving time was introduced in the United States, which fought in World War I, but it was abolished immediately after the war.
  2. In 1942, during World War II, daylight saving time was introduced in the United States. The beginning and end of daylight saving time (dates) are determined by each state from 1945 to 1966. In 1966, the federal government reunified the start and end times of daylight saving time.
  3. Daylight saving time began in most of Europe in 1976, three years after the fourth Middle East war led to the first oil shock (1973).
  4. Seeing the benefits of daylight saving time, 110 countries around the world followed, including China.

Obviously, saving money is a good thing that everyone likes.

Advantages of daylight saving time

Why is daylight saving time more energy efficient? As we all know, summer is the season of the year, the dawn is earlier, the dark is slower, the night is shorter, the day is longer. So, if people can get up early in the summer and stay up an hour later, they will make the most of the natural light resources, and then they will save electricity for lighting. And over the summer, you’ll save a huge amount of energy per person.

The disadvantages of daylight saving time

  1. When daylight saving time begins and ends, people have to set all their timing devices up or down, a hassle in the days when everyone had mechanical watches or feature phones.
  2. When daylight saving time ends, certain times occur twice in the same day, all of which are prone to confusion. And it affects the time of the flight.

Daylight saving time works well in high latitudes, where the sun rises earlier in summer than in winter. But in the lower latitudes, daylight saving time not only has little effect, but also has many negative effects.

Summer nights at low latitudes, for example, can be hot and humid, making it difficult to fall asleep. At this time, if you want to get up early, it will reduce people’s sleep quality, lead to depression, thus affecting the quality of work, and damage the health of the body, and let people’s mood become more irritable, there are a series of adverse reactions. China, however, is a low-latitude country, so it is not suitable for daylight saving time.

China is also a large country, so across five time zones, from east to west, the difference is five hours. If you are required to get up 1 hour in advance, it is better to be in the eastern region, but it is better to be in the western region, which is equivalent to getting up before dawn… In this way, the quality of sleep is not affected, because the day is not bright when you get up, it is impossible to eat breakfast, so the use of lighting electricity, will still be consumed. And many cities in China are hot like big furnaces in summer, which means that the most energy consumption in China is not for lighting, but for cooling! So, if daylight saving time is implemented in China, especially after a large number of fans and air conditioners appear and popularize, it will not be worth the loss to consume refrigeration electricity in order to save lighting electricity.

The original intention of daylight saving time is early sleep get up early, make full use of sunshine, and adjust fast or adjust slow all timing instrument, achieve this one purpose, it is the most inappropriate undoubtedly, be like to cover one’s ears and steal a bell. What we should do is to adjust the appropriate work and rest time and develop daily energy-saving and environmental protection methods such as turning off the lights.

3. The history of daylight saving time in China

Seeing the benefits of daylight saving time, 110 countries around the world have implemented daylight saving time, including China. In order to accelerate economic development and save energy, it issued a notice in April 1986 to implement daylight saving time in the whole country, with reference to the relevant programs mature abroad. But six years later, in 1991, China stopped daylight saving time.

The following table is the schedule of the previous implementation of daylight saving time in China:

  • From 1935 to 1951, each year on May 1 solstice September 30.
  • March 1, 1952 BBB 0 October 31.
  • From 1953 to 1954, each year on April 1 solstice October 31.
  • From 1955 to 1956, each year on May 1 solstice on September 30.
  • From 1957 to 1959, each year on April 1 solstice September 30.
  • From 1960 to 1961, every year on June 1 solstice on September 30.
  • From 1974 to 1975, each year on April 1 solstice October 31.
  • July 1, 1979 solstice September 30.
  • April 13, 1986 solstice September 14,
  • April 12, 1987 solstice September 13,
  • April 10, 1988 solstice September 11,
  • April 16, 1989 solstice September 17,
  • April 15, 1990 solstice September 16,
  • April 14, 1991 solstice September 15.

4. How to query the daylight saving time of a country in GausSDB (DWS)

4.1. Time zone related system tables in GausSDB (DWS)

Pg_timezone_names – System table in GausSDB (DWS) that stores timezone information

System table in pg_timezone_abbrevs-gaussdb (DWS) to store timezone abbreviation information

Select time zone where (2021/03/05) is already using daylight saving time

Select * from pg_timezone_names where (2021/03/05) timezone is already using daylight saving time:

postgres=# select * from pg_timezone_names where is_dst='t'; name | abbrev | utc_offset | is_dst -----------------------+--------+------------+-------- Australia/NSW | AEDT | 11:00:00 | t Australia/South | ACDT | 10:30:00 | t Australia/Yancowinna | ACDT | 10:30:00 | t Australia/Broken_Hill | ACDT | 10:30:00 | t Australia/Lord_Howe | +11 | 11:00:00 | t Australia/ACT | AEDT | 11:00:00 | t Australia/Melbourne | AEDT | 11:00:00 | t Australia/Adelaide | ACDT | 10:30:00 | t Australia/LHI | +11 | 11:00:00 | t Australia/Currie | AEDT | 11:00:00 | t Australia/Hobart | AEDT | 11:00:00 | t Australia/Tasmania | AEDT | 11:00:00 | t Australia/Sydney | AEDT |  11:00:00 | t Australia/Canberra | AEDT | 11:00:00 | t Australia/Victoria | AEDT | 11:00:00 | t NZ | NZDT | 13:00:00 | t  NZ-CHAT | +1345 | 13:45:00 | t Europe/Dublin | GMT | 00:00:00 | t Eire | GMT | 00:00:00 | t Chile/Continental | -03 | -03:00:00 | t Chile/EasterIsland | -05 | -05:00:00 | t Antarctica/McMurdo | NZDT | 13:00:00 | t Antarctica/South_Pole | NZDT | 13:00:00 | t America/Asuncion | -03 | -03:00:00 | t America/Santiago | -03 | -03:00:00 | t Pacific/Apia | +14 | 14:00:00 | t Pacific/Chatham | +1345 | 13:45:00 | t Pacific/Easter | -05 | -05:00:00 | t Pacific/Auckland | NZDT | 13:00:00 | t Pacific/Norfolk | +12 | 12:00:00 | t (30 rows)

Select * from pg_timezone_abbrevs where (2021/03/05) timezone is already using daylight saving time:

postgres=# select * from pg_timezone_abbrevs where is_dst='t'; abbrev | utc_offset | is_dst --------+------------+-------- ACDT | 10:30:00 | t ACSST | 10:30:00 | t ADT | -03:00:00 | t  AEDT | 11:00:00 | t AESST | 11:00:00 | t AKDT | -08:00:00 | t ALMST | 07:00:00 | t AWSST | 09:00:00 | t AZOST | 00:00:00 | t BDST | 02:00:00 | t BRST | -02:00:00 | t BST | 01:00:00 | t CADT | 10:30:00 | t CDT | -05:00:00 | t CEST | 02:00:00 | t CETDST | 02:00:00 | t CHADT | 13:45:00 | t CLST | -03:00:00 | t CLT | -03:00:00 | t EASST | -05:00:00 | t EAST | -05:00:00 | t EDT | -04:00:00 | t EEST | 03:00:00 | t EETDST | 03:00:00 | t EGST | 00:00:00 | t FJST | 13:00:00 |  t FNST | -01:00:00 | t IDT | 03:00:00 | t KDT | 10:00:00 | t KGST | 06:00:00 | t LHDT | 11:00:00 | t MDT | -06:00:00 | t MEST | 02:00:00 | t MESZ | 02:00:00 | t METDST | 02:00:00 | t MSD | 04:00:00 | t MUST | 05:00:00 | t NDT | -02:30:00 |  t NZDT | 13:00:00 | t PDT | -07:00:00 | t PKST | 06:00:00 | t PMDT | -02:00:00 | t PYST | -03:00:00 | t PYT | -03:00:00  | t SADT | 10:30:00 | t ULAST | 09:00:00 | t UYST | -02:00:00 | t UZST | 06:00:00 | t WADT | 08:00:00 | t WDT | 09:00:00 | t WETDST | 01:00:00 | t WGST | -02:00:00 | t YEKST | 06:00:00 | t (53 rows)

SQL > select * from GAUSSDB (DWS) where a time zone is in daylight saving time

In GausSDB (DWS) we can use SQL to query whether a time zone has adopted daylight saving time, but if we want to know when a time zone has historically used daylight saving time, we can use external tools to do this.

Zdump is a binary time file parser that comes with the Linux operating system. It allows you to parse a binary time zone file to see the time difference between a time zone and UTC and daylight saving time rules.

Binary time zone files in GAUSSDB (DWS) can also be parsed using the tool because of the standard time zone data repository that is consistent with GNU. From the picture above, we can see the history of our country’s adoption of daylight saving time.

5. To summarize

In summary, GausSDB (DWS), as a high-performance analytical database product for global users, supports Daylight Saving Time in line with industry standards and specifications. GAUSSDB (DWS) has its own time zone information database, you can easily query daylight saving time information.

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