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“I thought that Time is a theif stolen many things from me.Actually Time is a gift,Given then taken.”春光不自留,莫怪DongFeng恶。请抛开逸事剧情,只看wuliAnne海瑟微盛世美颜和特效!回去默默重温阿丽丝…


Time Zones

create table tb(ID int,Time datetime)
insert tb select 1,'2005/01/24 16:20'
union all select 2,'2005/01/23 22:45'
union all select 3,'2005/01/23 0:30'
union all select 4,'2005/01/21 4:28'
union all select 5,'2005/01/20 13:22'
只看颜就好。union all select 6,'2005/01/19 20:30'
union all select 7,'2005/01/19 18:23'
union all select 8,'2005/01/18 9:14'
union all select 9,'2005/01/18 18:04'

Prior to the late nineteenth century, time keeping was a purely local phenomenon. Each town would set their clocks to noon when the sun reached its zenith each day. A clockmaker or town clock would be the "official" time and the citizens would set their pocket watches and clocks to the time of the town - enterprising citizens would offer their services as mobile clock setters, carrying a watch with the accurate time to adjust the clocks in customer's homes on a weekly basis. Travel between cities meant having to change one's pocket watch upon arrival.
However, once railroads began to operate and move people rapidly across great distances, time became much more critical. In the early years of the railroads, the schedules were very confusing because each stop was based on a different local time. The standardization of time was essential to efficient operation of railroads.

select     case when grouping(b.Time)=1 then 'Total' else b.Time end,
    [Mon]=sum(case a.week when 1 then 1 else 0 end),
    [Tue]=sum(case a.week when 2 then 1 else 0 end),
    [Wed]=sum(case a.week when 3 then 1 else 0 end),
    [Thu]=sum(case a.week when 4 then 1 else 0 end),
    [Fri]=sum(case a.week when 5 then 1 else 0 end),
    [Sat]=sum(case a.week when 6 then 1 else 0 end),
    [Sun]=sum(case a.week when 0 then 1 else 0 end),
    select Time=convert(char(5),dateadd(hour,-1,Time),108)
        ,week=(@@datefirst datepart(weekday,Time)-1)%7
    from tb
)a right join(
    select id=1,a='16:00',b='19:59',Time='[5pm - 9pm)' union all
    select id=2,a='20:00',b='23:59',Time='[9pm - 1am)' union all
    select id=3,a='00:00',b='02:59',Time='[1am - 4am)' union all
    select id=4,a='03:00',b='07:29',Time='[4am - 8:30am)' union all
    select id=5,a='07:30',b='11:59',Time='[8:30am - 1pm)' union all
    select id=6,a='12:00',b='15:59',Time='[1pm - 5pm)'
)b on a.Time>=b.a and a.Time<b.b
group by b.id,b.Time with rollup
having grouping(b.Time)=0 or grouping(b.id)=1

In 1878, Canadian Sir Sanford Fleming proposed the system of worldwide time zones that we use today. He recommended that the world be divided into twenty-four time zones, each spaced 15 degrees of longitude apart. Since the earth rotates once every 24 hours and there are 360 degrees of longitude, each hour the earth rotates one-twenty-fourth of a circle or 15° of longitude. Sir Fleming's time zones were heralded as a brilliant solution to a chaotic problem worldwide.

drop table tb

United States railroad companies began utilizing Fleming's standard time zones on November 18, 1883. In 1884 an International Prime Meridian Conference was held in Washington D.C. to standardize time and select the Prime Meridian. The conference selected the longitude of Greenwich, England as zero degrees longitude and established the 24 time zones based on the Prime Meridian. Although the time zones had been established, not all countries switched immediately. Though most U.S. states began to adhere to the Pacific, Mountain, Central, and Eastern time zones by 1895, Congress didn't make the use of these time zones mandatory until the Standard Time Act of 1918.


Today, many countries operate on variations of the time zones proposed by Sir Fleming. All of China (which should span five time zones) uses a single time zone - eight hours ahead of Coordinated Universal Time (known by the abbreviation UTC - based on the time zone running through Greenwich at 0° longitude). Russia adheres to its designated time zones although the entire country is on permanent Daylight Saving Time and is an hour ahead of their actual zones. Australia uses three time zones - its central time zone is a half-hour ahead of its designated time zone. Several countries in the Middle East and South Asia also utilize half-hour time zones.


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