我想提供与当前时间和UTC时间之间的日期转换相关的代码，包括当前和历史日期，包括日光节省时间。我回顾了一些最近发布的帖子，但找不到我想要的解决方案，所以我总结了我发现的解决方案来开发自己的解决方案。我在SQL Server 2008R2中运行我的代码。在每个函数之前，测试用例作为注释提供。请随时查看相关帖子的Credits部分，试用我的代码，如果我遗漏了任何内容，请告诉我。感谢。
-- Test 1: select dbo.fn_isDayLightSavings(CAST('2014-01-01' AS DATE)), expect 0
-- Test 2: select dbo.fn_isDayLightSavings(CAST('2014-04-14' AS DATE)), expect 1
IF OBJECT_ID(N'fn_isDayLightSavings') IS NOT NULL AND OBJECTPROPERTY(OBJECT_ID(N'fn_isDayLightSavings'),'IsScalarFunction') = 1
DROP FUNCTION fn_isDayLightSavings;
GO
CREATE FUNCTION fn_isDayLightSavings (@dt AS DATETIME)
RETURNS TINYINT
AS
BEGIN
DECLARE @rtn TINYINT, @year INT, @dtsStartMonth DATETIME, @dtsEndMonth DATETIME, @dstStart DATETIME, @dstEnd DATETIME;
SET @year = DATEPART(YEAR, @dt);
-- In year 2007, US day light savings period changes from Apr-Oct to Mar-Nov.
if @year < 2007
BEGIN
-- Last Sunday of April at 2 AM
SET @dtsStartMonth = DATEADD(MONTH, 4, DATEADD(YEAR, @year - 1900, 0));
SET @dstStart = DATEADD(HOUR, 2, DATEADD(day, -(DATEPART(dw, @dtsStartMonth) - 1), @dtsStartMonth));
-- Last Sunday of October at 2 AM
SET @dtsEndMonth = DATEADD(MONTH, 10, DATEADD(YEAR, @year - 1900, 0));
SET @dstEnd = DATEADD(HOUR, 2, DATEADD(day, -(DATEPART(dw, @dtsEndMonth) - 1), @dtsEndMonth));
END
else
BEGIN
-- 2nd Sunday of March at 2 AM
SET @dtsStartMonth = DATEADD(MONTH, 2, DATEADD(YEAR, @year - 1900, 0));
SET @dstStart = DATEADD(HOUR, 2, DATEADD(day, ((15 - DATEPART(dw, @dtsStartMonth)) % 7) + 7, @dtsStartMonth));
-- 1st Sunday of November at 2 AM
SET @dtsEndMonth = DATEADD(MONTH, 10, DATEADD(YEAR, @year - 1900, 0));
SET @dstEnd = DATEADD(HOUR, 2, DATEADD(day, ((8 - DATEPART(dw, @dtsEndMonth)) % 7) + 7, @dtsEndMonth));
END
if @dt BETWEEN @dstStart AND @dstEnd SET @rtn=1 ELSE SET @rtn=0;
RETURN @rtn;
END
GO
-- Test 1: select dbo.fn_DateTime2UTC(CAST('2014-01-01 01:00:00' AS DATETIME), 0), expect '2014-01-01 07:00:00.000'
-- Test 2: select dbo.fn_DateTime2UTC(CAST('2014-01-01 01:00:00' AS DATETIME), 1), expect '2013-01-01 07:00:00.000'
-- Test 3: select dbo.fn_DateTime2UTC(CAST('2014-05-01 01:00:00' AS DATETIME), 0), expect '2014-05-01 06:00:00.000'
-- Test 4: select dbo.fn_DateTime2UTC(CAST('2014-05-01 01:00:00' AS DATETIME), 1), expect '2014-05-01 07:00:00.000'
IF OBJECT_ID(N'fn_DateTime2UTC') IS NOT NULL AND OBJECTPROPERTY(OBJECT_ID(N'fn_DateTime2UTC'),'IsScalarFunction') = 1
DROP FUNCTION fn_DateTime2UTC;
GO
CREATE FUNCTION fn_DateTime2UTC (@dt AS DATETIME, @ignoreDST AS TINYINT = 0)
-- do CAST(? AS DATETIMEOFFSET), if need datetimeoffset type
RETURNS DATETIME
AS
BEGIN
DECLARE @tzOffset INT, @utcDt DATETIME;
-- Get current time zone offset in minutes
SET @tzOffset = DATEPART(TZoffset, SYSDATETIMEOFFSET()) +
(CASE WHEN dbo.fn_isDayLightSavings(@dt)=1 THEN 60 ELSE 0 END);
if dbo.fn_isDayLightSavings(@dt)=0
set @utcDt = DATEADD(MINUTE, -@tzOffset, @dt);
else if @ignoreDST=0
set @utcDt = DATEADD(MINUTE, -@tzOffset, @dt);
else
set @utcDt = DATEADD(MINUTE, -@tzOffset+60, @dt);
return @utcDt;
END
GO
-- Test 1: select dbo.fn_UTC2DateTime(CAST('2014-01-01 07:00:00.000' AS DATETIME), 0), expect '2014-01-01 01:00:00'
-- Test 2: select dbo.fn_UTC2DateTime(CAST('2013-01-01 07:00:00.000' AS DATETIME), 1), expect '2014-01-01 01:00:00'
-- Test 3: select dbo.fn_UTC2DateTime(CAST('2014-05-01 06:00:00.000' AS DATETIME), 0), expect '2014-05-01 01:00:00'
-- Test 4: select dbo.fn_UTC2DateTime(CAST('2014-05-01 07:00:00.000' AS DATETIME), 1), expect '2014-05-01 01:00:00'
IF OBJECT_ID(N'fn_UTC2DateTime') IS NOT NULL AND OBJECTPROPERTY(OBJECT_ID(N'fn_UTC2DateTime'),'IsScalarFunction') = 1
DROP FUNCTION fn_UTC2DateTime;
GO
CREATE FUNCTION fn_UTC2DateTime (@utcDt AS DATETIME, @ignoreDST AS TINYINT = 0)
RETURNS DATETIME
AS
BEGIN
DECLARE @tzOffset INT, @dt DATETIME;
-- Get current time zone offset in minutes
SET @tzOffset = DATEPART(TZoffset, SYSDATETIMEOFFSET()) +
(CASE WHEN dbo.fn_isDayLightSavings(@utcDt)=1 THEN 60 ELSE 0 END);
if dbo.fn_isDayLightSavings(@utcDt)=0
set @dt = DATEADD(MINUTE, @tzOffset, @utcDt);
else if @ignoreDST=0
set @dt = DATEADD(MINUTE, @tzOffset, @utcDt);
else
set @dt = DATEADD(MINUTE, @tzOffset-60, @utcDt);
return @dt;
END
GO
-- Test 1: select dbo.fn_UTC2DateTimeOffset(CAST('2014-01-01 07:00:00.000' AS DATETIME), 0), expect '2014-01-01 01:00:00.0000000 -06:00'
-- Test 2: select dbo.fn_UTC2DateTimeOffset(CAST('2013-01-01 07:00:00.000' AS DATETIME), 1), expect '2014-01-01 01:00:00.0000000 -06:00'
-- Test 3: select dbo.fn_UTC2DateTimeOffset(CAST('2014-05-01 06:00:00.000' AS DATETIME), 0), expect '2014-05-01 01:00:00.0000000 -05:00'
-- Test 4: select dbo.fn_UTC2DateTimeOffset(CAST('2014-05-01 07:00:00.000' AS DATETIME), 1), expect '2014-05-01 00:00:00.0000000 -06:00'
IF OBJECT_ID(N'fn_UTC2DateTimeOffset') IS NOT NULL AND OBJECTPROPERTY(OBJECT_ID(N'fn_UTC2DateTimeOffset'),'IsScalarFunction') = 1
DROP FUNCTION fn_UTC2DateTimeOffset;
GO
CREATE FUNCTION fn_UTC2DateTimeOffset (@utcDt AS DATETIME, @ignoreDST TINYINT = 0)
RETURNS DATETIMEOFFSET
AS
BEGIN
DECLARE @tzOffset INT, @dt DATETIMEOFFSET;
-- Get current time zone offset in minutes
SET @tzOffset = DATEPART(TZoffset, SYSDATETIMEOFFSET()) +
(CASE WHEN dbo.fn_isDayLightSavings(@utcDt)=1 THEN 60 ELSE 0 END);
if dbo.fn_isDayLightSavings(@utcDt)=0
set @dt = SWITCHOFFSET(CAST(@utcDt AS DATETIMEOFFSET), @tzOffset);
else if @ignoreDST=0
set @dt = SWITCHOFFSET(CAST(@utcDt AS DATETIMEOFFSET), @tzOffset);
else
set @dt = SWITCHOFFSET(CAST(@utcDt AS DATETIMEOFFSET), @tzOffset-60);
return @dt;
END
GO
-- Credits:
-- Determination of day light savings start and end time, Jamie F., 11/1/2013
-- (http://stackoverflow.com/questions/19732896/how-to-create-daylight-savings-time-start-and-end-function-in-sql-server)
-- Day light savings time calendar, USNO
-- (http://aa.usno.navy.mil/faq/docs/daylight_time.php)
-- Time zone offset, Microsoft
-- (http://msdn.microsoft.com/en-us/library/ms174420.aspx)
-- Local system date time with time zone, Robert Cantor, 12/7/2013
-- (http://stackoverflow.com/questions/1205142/tsql-how-to-convert-local-time-to-utc-sqlserver2008)
-- Convert date with time zone and day light savings, Eric Z Beard, 8/24/2008
-- (http://stackoverflow.com/questions/24797/effectively-converting-dates-between-utc-and-local-ie-pst-time-in-sql-2005#25073)
答案 0 :(得分：0)
感谢您将这些知识汇集到一个地方。假设它是准确的，它很容易立即拿起和使用。
然而，问题在于，如果没有大量的单元测试，您无法确定准确性。
我可能会建议日期/时间转换的最佳选择是使用现有的高度测试的开源库，例如http://nodatime.org/。日期/时间转换有许多内部和细节，不可能包含在几十行SQL代码中。
nodatime是一个.NET库，可以通过SQL Server CLR用户定义的函数功能轻松访问。