Это отработка работы, проделанной Даниэлем Литтлом для этого вопроса, но с учетом перехода на летнее время (работает для дат 01-01 1902 и выше из-за ограничения int для функции dateadd):
Сначала нам нужно создать таблицу, в которой будут храниться диапазоны дат для летнего времени (источник: История времени в Соединенных Штатах ):
CREATE TABLE [dbo].[CFG_DAY_LIGHT_SAVINGS_TIME](
[BEGIN_DATE] [datetime] NULL,
[END_DATE] [datetime] NULL,
[YEAR_DATE] [smallint] NULL
) ON [PRIMARY]
GO
INSERT INTO CFG_DAY_LIGHT_SAVINGS_TIME VALUES
('2001-04-01 02:00:00.000', '2001-10-27 01:59:59.997', 2001),
('2002-04-07 02:00:00.000', '2002-10-26 01:59:59.997', 2002),
('2003-04-06 02:00:00.000', '2003-10-25 01:59:59.997', 2003),
('2004-04-04 02:00:00.000', '2004-10-30 01:59:59.997', 2004),
('2005-04-03 02:00:00.000', '2005-10-29 01:59:59.997', 2005),
('2006-04-02 02:00:00.000', '2006-10-28 01:59:59.997', 2006),
('2007-03-11 02:00:00.000', '2007-11-03 01:59:59.997', 2007),
('2008-03-09 02:00:00.000', '2008-11-01 01:59:59.997', 2008),
('2009-03-08 02:00:00.000', '2009-10-31 01:59:59.997', 2009),
('2010-03-14 02:00:00.000', '2010-11-06 01:59:59.997', 2010),
('2011-03-13 02:00:00.000', '2011-11-05 01:59:59.997', 2011),
('2012-03-11 02:00:00.000', '2012-11-03 01:59:59.997', 2012),
('2013-03-10 02:00:00.000', '2013-11-02 01:59:59.997', 2013),
('2014-03-09 02:00:00.000', '2014-11-01 01:59:59.997', 2014),
('2015-03-08 02:00:00.000', '2015-10-31 01:59:59.997', 2015),
('2016-03-13 02:00:00.000', '2016-11-05 01:59:59.997', 2016),
('2017-03-12 02:00:00.000', '2017-11-04 01:59:59.997', 2017),
('2018-03-11 02:00:00.000', '2018-11-03 01:59:59.997', 2018),
('2019-03-10 02:00:00.000', '2019-11-02 01:59:59.997', 2019),
('2020-03-08 02:00:00.000', '2020-10-31 01:59:59.997', 2020),
('2021-03-14 02:00:00.000', '2021-11-06 01:59:59.997', 2021),
('2022-03-13 02:00:00.000', '2022-11-05 01:59:59.997', 2022),
('2023-03-12 02:00:00.000', '2023-11-04 01:59:59.997', 2023),
('2024-03-10 02:00:00.000', '2024-11-02 01:59:59.997', 2024),
('2025-03-09 02:00:00.000', '2025-11-01 01:59:59.997', 2025),
('1967-04-30 02:00:00.000', '1967-10-29 01:59:59.997', 1967),
('1968-04-28 02:00:00.000', '1968-10-27 01:59:59.997', 1968),
('1969-04-27 02:00:00.000', '1969-10-26 01:59:59.997', 1969),
('1970-04-26 02:00:00.000', '1970-10-25 01:59:59.997', 1970),
('1971-04-25 02:00:00.000', '1971-10-31 01:59:59.997', 1971),
('1972-04-30 02:00:00.000', '1972-10-29 01:59:59.997', 1972),
('1973-04-29 02:00:00.000', '1973-10-28 01:59:59.997', 1973),
('1974-01-06 02:00:00.000', '1974-10-27 01:59:59.997', 1974),
('1975-02-23 02:00:00.000', '1975-10-26 01:59:59.997', 1975),
('1976-04-25 02:00:00.000', '1976-10-31 01:59:59.997', 1976),
('1977-04-24 02:00:00.000', '1977-10-31 01:59:59.997', 1977),
('1978-04-30 02:00:00.000', '1978-10-29 01:59:59.997', 1978),
('1979-04-29 02:00:00.000', '1979-10-28 01:59:59.997', 1979),
('1980-04-27 02:00:00.000', '1980-10-26 01:59:59.997', 1980),
('1981-04-26 02:00:00.000', '1981-10-25 01:59:59.997', 1981),
('1982-04-25 02:00:00.000', '1982-10-25 01:59:59.997', 1982),
('1983-04-24 02:00:00.000', '1983-10-30 01:59:59.997', 1983),
('1984-04-29 02:00:00.000', '1984-10-28 01:59:59.997', 1984),
('1985-04-28 02:00:00.000', '1985-10-27 01:59:59.997', 1985),
('1986-04-27 02:00:00.000', '1986-10-26 01:59:59.997', 1986),
('1987-04-05 02:00:00.000', '1987-10-25 01:59:59.997', 1987),
('1988-04-03 02:00:00.000', '1988-10-30 01:59:59.997', 1988),
('1989-04-02 02:00:00.000', '1989-10-29 01:59:59.997', 1989),
('1990-04-01 02:00:00.000', '1990-10-28 01:59:59.997', 1990),
('1991-04-07 02:00:00.000', '1991-10-27 01:59:59.997', 1991),
('1992-04-05 02:00:00.000', '1992-10-25 01:59:59.997', 1992),
('1993-04-04 02:00:00.000', '1993-10-31 01:59:59.997', 1993),
('1994-04-03 02:00:00.000', '1994-10-30 01:59:59.997', 1994),
('1995-04-02 02:00:00.000', '1995-10-29 01:59:59.997', 1995),
('1996-04-07 02:00:00.000', '1996-10-27 01:59:59.997', 1996),
('1997-04-06 02:00:00.000', '1997-10-26 01:59:59.997', 1997),
('1998-04-05 02:00:00.000', '1998-10-25 01:59:59.997', 1998),
('1999-04-04 02:00:00.000', '1999-10-31 01:59:59.997', 1999),
('2000-04-02 02:00:00.000', '2000-10-29 01:59:59.997', 2000)
GO
Теперь мы создаем функцию для каждого американского часового пояса. Это при условии, что время Unix в миллисекундах. Если это в секундах, удалите / 1000 из кода:
Pacific
create function [dbo].[UnixTimeToPacific]
(@unixtime bigint)
returns datetime
as
begin
declare @pacificdatetime datetime
declare @interimdatetime datetime = dateadd(s, @unixtime/1000, '1970-01-01')
select @pacificdatetime = dateadd(hour,case when @interimdatetime between begin_date and end_date then -7 else -8 end ,@interimdatetime)
from cfg_day_light_savings_time where year_date = datepart(year,@interimdatetime)
if @pacificdatetime is null
select @pacificdatetime= dateadd(hour, -7, @interimdatetime)
return @pacificdatetime
end
Восточная
create function [dbo].[UnixTimeToEastern]
(@unixtime bigint)
returns datetime
as
begin
declare @easterndatetime datetime
declare @interimdatetime datetime = dateadd(s, @unixtime/1000, '1970-01-01')
select @easterndatetime = dateadd(hour,case when @interimdatetime between begin_date and end_date then -4 else -5 end ,@interimdatetime)
from cfg_day_light_savings_time where year_date = datepart(year,@interimdatetime)
if @easterndatetime is null
select @easterndatetime= dateadd(hour, -4, @interimdatetime)
return @easterndatetime
end
Central
create function [dbo].[UnixTimeToCentral]
(@unixtime bigint)
returns datetime
as
begin
declare @centraldatetime datetime
declare @interimdatetime datetime = dateadd(s, @unixtime/1000, '1970-01-01')
select @centraldatetime = dateadd(hour,case when @interimdatetime between begin_date and end_date then -5 else -6 end ,@interimdatetime)
from cfg_day_light_savings_time where year_date = datepart(year,@interimdatetime)
if @centraldatetime is null
select @centraldatetime= dateadd(hour, -5, @interimdatetime)
return @centraldatetime
end
Mountain
create function [dbo].[UnixTimeToMountain]
(@unixtime bigint)
returns datetime
as
begin
declare @mountaindatetime datetime
declare @interimdatetime datetime = dateadd(s, @unixtime/1000, '1970-01-01')
select @mountaindatetime = dateadd(hour,case when @interimdatetime between begin_date and end_date then -6 else -7 end ,@interimdatetime)
from cfg_day_light_savings_time where year_date = datepart(year,@interimdatetime)
if @mountaindatetime is null
select @mountaindatetime= dateadd(hour, -6, @interimdatetime)
return @mountaindatetime
end
Гавайи
create function [dbo].[UnixTimeToHawaii]
(@unixtime bigint)
returns datetime
as
begin
declare @hawaiidatetime datetime
declare @interimdatetime datetime = dateadd(s, @unixtime/1000, '1970-01-01')
select @hawaiidatetime = dateadd(hour,-10,@interimdatetime)
from cfg_day_light_savings_time where year_date = datepart(year,@interimdatetime)
return @hawaiidatetime
end
Arizona
create function [dbo].[UnixTimeToArizona]
(@unixtime bigint)
returns datetime
as
begin
declare @arizonadatetime datetime
declare @interimdatetime datetime = dateadd(s, @unixtime/1000, '1970-01-01')
select @arizonadatetime = dateadd(hour,-7,@interimdatetime)
from cfg_day_light_savings_time where year_date = datepart(year,@interimdatetime)
return @arizonadatetime
end
Alaska
create function [dbo].[UnixTimeToAlaska]
(@unixtime bigint)
returns datetime
as
begin
declare @alaskadatetime datetime
declare @interimdatetime datetime = dateadd(s, @unixtime/1000, '1970-01-01')
select @alaskadatetime = dateadd(hour,case when @interimdatetime between begin_date and end_date then -8 else -9 end ,@interimdatetime)
from cfg_day_light_savings_time where year_date = datepart(year,@interimdatetime)
if @alaskadatetime is null
select @alaskadatetime= dateadd(hour, -8, @interimdatetime)
return @alaskadatetime
end