Temporary variable in UTC Time in T-SQL - sql

I am trying to convert a temporary variable into UTC time and print it using the following,
declare #dt datetime, #dtEnd datetime
set #dt = '2017-04-25' AT TIME ZONE 'UTC'
set #dtEnd = '2017-04-30' AT TIME ZONE 'UTC'
select dateadd(day, number, #dt)
from
(select distinct number from master.dbo.spt_values
where name is null
) n
where dateadd(day, number, #dt) < #dtEnd
I got this code from the accepted answer here.
I am getting an error,
Argument data type varchar is invalid for argument 1 of AT TIME ZONE
function.
I am using SQL Server docs to convert from CDT to UTC. Linked answer works great to just print without AT TIME ZONE 'UTC'.
How can I convert a temporary variable to print in UTC time?


You need to use cast as datetime
declare #dt datetime, #dtEnd datetime
set #dt = CAST('2017-04-25' AS DATETIME) AT TIME ZONE 'Central Standard Time' AT TIME ZONE 'UTC'
set #dtEnd = CAST('2017-04-30' AS DATETIME) AT TIME ZONE 'Central Standard Time' AT TIME ZONE 'UTC'
select dateadd(day, number, #dt)
from
(select distinct number from master.dbo.spt_values
where name is null
) n
where dateadd(day, number, #dt) < #dtEnd

Related

SFMC date timezone

Can we convert Dataview Sent/Open CST date to UTC timezone without using dateadd funtion. Any other timezone related function?

Yes, with AT TIME ZONE.
Here's an example from SFSE:
SELECT
t.mailingState
, v.specificUTCDateTime
, case
when t.mailingState = 'AB' then convert(datetime2, v.specificUTCDateTime at time zone 'MOUNTAIN STANDARD TIME')
when t.mailingState = 'VC' then convert(datetime2, v.specificUTCDateTime at time zone 'PACIFIC STANDARD TIME')
end adjSendDate
from timezones_canada t
outer apply (
select
SMALLDATETIMEFROMPARTS(YEAR(GETUTCDate()), MONTH(GETUTCDate()), DAY(GETUTCDate()), 19, 30) AT TIME ZONE 'UTC' specificUTCDateTime
) v

Append time from table to getdate() while using case

I am trying to append time from a column to a date and use in a case statment
getdate() at time zone 'Central Standard Time'
this is what i've tried so far
select case when
getdate() at time zone 'Central Standard Time' <=
cast(cast (getdate() at time zone 'Central Standard Time'as date) as datetime) + endtime from tablename where id = 'uniqueid'
1 else 0 end
datatype of endtime column is nvarchar and the format of the time is 21:00
and this is the error that i am getting
Incorrect syntax near the keyword 'from'
I have tried using this solution as well https://stackoverflow.com/a/700647 but still the same error. But when i do
select CAST(CAST(getdate() at time zone 'Central Standard Time' AS DATE) AS DATETIME) + endtime from tablename where id = 'uniqueid'
i get a proper response of 2020-01-07 07:00:00.000
and this seems to work fine as well
select case when
getdate() at time zone 'Central Standard Time' >=
CAST(CAST(CAST(getdate() at time zone 'Central Standard Time'AS DATE) AS DATETIME) + '' + '10:00'as DATETIME)
then 1 else 0
end
returns 1
but
select case when
getdate() at time zone 'Central Standard Time' <=
cast(CAST(CAST(getdate() at time zone 'Central Standard Time' AS DATE) AS DATETIME) + endtime from table where id = 'uniqueid' as datetime)
then 1 else 0 end
returns Incorrect syntax near the keyword 'where'
I am not sure if i am doing something wrong or is it a limitation.

The big issue is that you are trying to use a subquery without using a subquery, which is what the syntax error is all about. Try this instead (expanded out for clarity)
SELECT
CASE
WHEN getdate() at TIME zone 'Central Standard Time' <=
(SELECT cast(cast(getdate() at TIME zone 'Central Standard Time' AS DATE) AS DATETIME) + endtime FROM tablename WHERE id = 'uniqueid') -- Subquery
THEN 1
ELSE 0
END

T-SQL: Convert the value of datetime field from UTC to CET timezone

I have a DB that stores dates as datetime with UTC offset.
How do I convert these dates from UTC to say CET in a select statement?
And is there are some kind of syntax sugar that takes care of the whole daylight autumn/winter and springs/summer offset thing?
EDIT:
I've found this library on CodePlex useful:
DateTimeUtil
A set of UDFs and configuration data for extended datetime handling, e. g. it offers easy timezone conversion incl. support for daylight saving times using native T-SQL (no CLRs).

SELECT CONVERT(VARCHAR, dbo.udfToLocalTime(t.CreatedDateTime, '1'), 113)
FROM yourtable t
In case of update:
UPDATE yourtable t
SET t.CreatedDateTime = CONVERT(VARCHAR, dbo.udfToLocalTime(t.CreatedDateTime, '1'), 113)
Use a UDF as below
CREATE FUNCTION udfToLocalTime
(
#UtcDateTimeAS DATETIME
,#UtcOffset AS INT = -8 --PST
)
RETURNS DATETIME
AS
BEGIN
DECLARE #PstDateTimeAS DATETIME
,#Year AS CHAR(4)
,#DstStart AS DATETIME
,#DstEndAS DATETIME
,#Mar1 AS DATETIME
,#Nov1 AS DATETIME
,#MarTime AS TIME
,#NovTime AS TIME
,#Mar1Day AS INT
,#Nov1Day AS INT
,#MarDiff AS INT
,#NovDiff AS INT
SELECT #Year = YEAR(#UtcDateTime)
,#MarTime = CONVERT(TIME, DATEADD(HOUR, -#UtcOffset, '1900-01-01 02:00'))
,#NovTime = CONVERT(TIME, DATEADD(HOUR, -#UtcOffset - 1, '1900-01-01 02:00'))
,#Mar1 = CONVERT(CHAR(16), #Year + '-03-01 ' + CONVERT(CHAR(5), #MarTime), 126)
,#Nov1 = CONVERT(CHAR(16), #Year + '-11-01 ' + CONVERT(CHAR(5), #NovTime), 126)
,#Mar1Day = DATEPART(WEEKDAY, #Mar1)
,#Nov1Day = DATEPART(WEEKDAY, #Nov1)
--Get number of days between Mar 1 and DST start date
IF #Mar1Day = 1
SET #MarDiff = 7
ELSE
SET #MarDiff = 15 - #Mar1Day
--Get number of days between Nov 1 and DST end date
IF #Nov1Day = 1
SET #NovDiff = 0
ELSE
SET #NovDiff = 8 - #Nov1Day
--Get DST start and end dates
SELECT #DstStart = DATEADD(DAY, #MarDiff, #Mar1)
,#DstEnd= DATEADD(DAY, #NovDiff, #Nov1)
--Change UTC offset if #UtcDateTime is in DST Range
IF #UtcDateTime >= #DstStart AND #UtcDateTime < #DstEnd
SET #UtcOffset = #UtcOffset + 1
--Get Conversion
SET #PstDateTime = DATEADD(HOUR, #UtcOffset, #UtcDateTime)
RETURN #PstDateTime
END

It's perfect if your DB contains UTC dates. Better way is to use your OS timezone offset.
For example:
select
dateadd(minute,DATEPART(TZ, SYSDATETIMEOFFSET()), YourUTCDate) as timestamp
from YourTable

Use the following function to convert Date TImeZones.
create or replace FUNCTION timezoneConverter
(v_date in date, inputDateZone in varchar2 default 'UTC', outputDateZone in varchar2 default 'UTC')
return date AS date_out date;
BEGIN
SELECT
to_date(
to_char(FROM_TZ(to_timestamp(to_char( v_date,'dd.mm.yyyy hh24:mi:ss' ),'dd.mm.yyyy hh24:mi:ss'),
to_char(inputDateZone)) AT TIME ZONE
to_char(outputDateZone),
'dd.mm.yyyy hh24:mi:ss'), 'dd.mm.yyyy hh24:mi:ss')
into date_out FROM dual;
return date_out;
EXCEPTION
when others then
DBMS_OUTPUT.put_line('Date:' || v_date || 'TZ:' || inputDateZone || '-' || outputDateZone || ' / ' || sqlcode || ' / ' || SQLERRM(sqlcode));
--date_out := to_date(to_char(v_date-1/24, 'yyyymmddhh24miss'), 'yyyymmddhh24miss');
date_out := null;
return date_out;
END;
/
DayLight Central European Time (CET) vs Central European Summer Time (CEST)
Short Hour 2nd hour skipped. Note: hours shift because clocks change forward 1 hour.
--set serveroutput on; -- View -> Dbms Output : set serveroutput on [serveroutput must be set ON or OFF or OPTIMIZED or UNOPTIMIZED]
SELECT
timezoneConverter(to_timestamp('2020-03-29T01:00Z', 'yyyy-mm-dd"T"hh24:mi"Z"'), 'CET', 'UTC') CETtoUTC1, -- 29-MAR-2020 00:00:00
timezoneConverter(to_timestamp('2020-03-29T02:00Z', 'yyyy-mm-dd"T"hh24:mi"Z"'), 'CET', 'UTC') CETtoUTC2, -- (null)
timezoneConverter(to_timestamp('2020-03-29T02:00Z', 'yyyy-mm-dd"T"hh24:mi"Z"'), 'UTC', 'CET') UTCtoCET FROM dual; -- 29-MAR-2020 04:00:00
-- Date:29-MAR-2020 02:00:00TZ:CET-UTC / -1878 / ORA-01878: specified field not found in datetime or interval
Long Hour 2nd hour repeats Note: hours shift because clocks change backward 1 hour.
SELECT
timezoneConverter(to_timestamp('2020-10-25T02:00Z', 'yyyy-mm-dd"T"hh24:mi"Z"'), 'UTC', 'CET') UTCtoCET, -- 25-OCT-2020 03:00:00
timezoneConverter(to_timestamp('2020-10-25T02:00Z', 'yyyy-mm-dd"T"hh24:mi"Z"'), 'CET', 'UTC') CETtoUTC2, -- 25-OCT-2020 01:00:00
timezoneConverter(to_timestamp('2020-10-25T01:00Z', 'yyyy-mm-dd"T"hh24:mi"Z"'), 'CET', 'UTC') CETtoUTC1 FROM dual; -- 24-OCT-2020 23:00:00
The following example converts the datetime value of one time zone to another time zone: docs.oracle.com
SELECT FROM_TZ(CAST(TO_DATE('1999-12-01 11:00:00',
'YYYY-MM-DD HH:MI:SS') AS TIMESTAMP), 'America/New_York')
AT TIME ZONE 'America/Los_Angeles' "West Coast Time"
FROM DUAL;
West Coast Time
------------------------------------------------
01-DEC-99 08.00.00.000000 AM AMERICA/LOS_ANGELES

Convert Datetime column from UTC to local time in select statement

I'm doing a few SQL select queries and would like to convert my UTC datetime column into local time to be displayed as local time in my query results. Note, I am NOT looking to do this conversion via code but rather when I am doing manual and random SQL queries against my databases.

You can do this as follows on SQL Server 2008 or greater:
SELECT CONVERT(datetime,
SWITCHOFFSET(CONVERT(datetimeoffset,
MyTable.UtcColumn),
DATENAME(TzOffset, SYSDATETIMEOFFSET())))
AS ColumnInLocalTime
FROM MyTable
You can also do the less verbose:
SELECT DATEADD(mi, DATEDIFF(mi, GETUTCDATE(), GETDATE()), MyTable.UtcColumn)
AS ColumnInLocalTime
FROM MyTable
Whatever you do, do not use - to subtract dates, because the operation is not atomic, and you will on occasion get indeterminate results due to race conditions between the system datetime and the local datetime being checked at different times (i.e., non-atomically).
Please note that this answer does not take DST into account. If you want to include a DST adjustment, please also see the following SO question:
How to create Daylight Savings time Start and End function in SQL Server

I didn't find any of these example helpful in getting a datetime stored as UTC to a datetime in a specified timezone (NOT the timezone of the server because Azure SQL databases run as UTC). This is how I handled it. It's not elegant but it's simple and gives you the right answer without maintaining other tables:
select CONVERT(datetime, SWITCHOFFSET(dateTimeField, DATEPART(TZOFFSET,
dateTimeField AT TIME ZONE 'Eastern Standard Time')))

If your local date time is say Eastern Standard Time and you want to convert from UTC to that, then in Azure SQL and SQL Server 2016 and above, you can do:
SELECT YourUtcColumn AT TIME ZONE 'UTC' AT TIME ZONE 'Eastern Standard Time' AS
LocalTime
FROM YourTable
The full list of timezone names can be found with:
SELECT * FROM sys.time_zone_info
And yes, the timezones are badly named - even though it is Eastern Standard Time, daylight savings is taken into account.

If you need a conversion other than your server's location, here is a function that allows you to pass a standard offset and accounts for US Daylight Savings Times:
-- =============================================
-- Author: Ron Smith
-- Create date: 2013-10-23
-- Description: Converts UTC to DST
-- based on passed Standard offset
-- =============================================
CREATE FUNCTION [dbo].[fn_UTC_to_DST]
(
#UTC datetime,
#StandardOffset int
)
RETURNS datetime
AS
BEGIN
declare
#DST datetime,
#SSM datetime, -- Second Sunday in March
#FSN datetime -- First Sunday in November
-- get DST Range
set #SSM = datename(year,#UTC) + '0314'
set #SSM = dateadd(hour,2,dateadd(day,datepart(dw,#SSM)*-1+1,#SSM))
set #FSN = datename(year,#UTC) + '1107'
set #FSN = dateadd(second,-1,dateadd(hour,2,dateadd(day,datepart(dw,#FSN)*-1+1,#FSN)))
-- add an hour to #StandardOffset if #UTC is in DST range
if #UTC between #SSM and #FSN
set #StandardOffset = #StandardOffset + 1
-- convert to DST
set #DST = dateadd(hour,#StandardOffset,#UTC)
-- return converted datetime
return #DST
END
GO

Using new SQL Server 2016 opportunities:
CREATE FUNCTION ToLocalTime(#dtUtc datetime, #timezoneId nvarchar(256))
RETURNS datetime
AS BEGIN
return #dtUtc AT TIME ZONE 'UTC' AT TIME ZONE #timezoneId
/* -- second way, faster
return SWITCHOFFSET(#dtUtc , DATENAME(tz, #dtUtc AT TIME ZONE #timezoneId))
*/
/* -- third way
declare #dtLocal datetimeoffset
set #dtLocal = #dtUtc AT TIME ZONE #timezoneId
return dateadd(minute, DATEPART (TZoffset, #dtLocal), #dtUtc)
*/
END
GO
But clr procedure works in 5 times faster :'-(
Pay attention that Offset for one TimeZone can change to winter or summer time. For example
select cast('2017-02-08 09:00:00.000' as datetime) AT TIME ZONE 'Eastern Standard Time'
select cast('2017-08-08 09:00:00.000' as datetime) AT TIME ZONE 'Eastern Standard Time'
results:
2017-02-08 09:00:00.000 -05:00
2017-08-08 09:00:00.000 -04:00
You can't just add constant offset.

If enabling CLR on your database is an option as well as using the sql server's timezone, it can be written in .Net quite easily.
public partial class UserDefinedFunctions
{
[Microsoft.SqlServer.Server.SqlFunction]
public static SqlDateTime fn_GetLocalFromUTC(SqlDateTime UTC)
{
if (UTC.IsNull)
return UTC;
return new SqlDateTime(UTC.Value.ToLocalTime());
}
}
A UTC datetime value goes in and the local datetime value relative to the server comes out. Null values return null.

None of these worked for me but this below worked 100%. Hope this can help others trying to convert it like I was.
CREATE FUNCTION [dbo].[fn_UTC_to_EST]
(
#UTC datetime,
#StandardOffset int
)
RETURNS datetime
AS
BEGIN
declare
#DST datetime,
#SSM datetime, -- Second Sunday in March
#FSN datetime -- First Sunday in November
-- get DST Range
set #SSM = DATEADD(dd,7 + (6-(DATEDIFF(dd,0,DATEADD(mm,(YEAR(GETDATE())-1900) * 12 + 2,0))%7)),DATEADD(mm,(YEAR(GETDATE())-1900) * 12 + 2,0))+'02:00:00'
set #FSN = DATEADD(dd, (6-(DATEDIFF(dd,0,DATEADD(mm,(YEAR(GETDATE())-1900) * 12 + 10,0))%7)),DATEADD(mm,(YEAR(GETDATE())-1900) * 12 + 10,0)) +'02:00:00'
-- add an hour to #StandardOffset if #UTC is in DST range
if #UTC between #SSM and #FSN
set #StandardOffset = #StandardOffset + 1
-- convert to DST
set #DST = dateadd(hour,#StandardOffset,#UTC)
-- return converted datetime
return #DST
END

Well if you store the data as UTC date in the database you can do something as simple as
select
[MyUtcDate] + getdate() - getutcdate()
from [dbo].[mytable]
this was it's always local from the point of the server and you are not fumbling with AT TIME ZONE 'your time zone name',
if your database get moved to another time zone like a client installation a hard coded time zone might bite you.

There is no simple way to do this in a correct AND generic way.
First of all it must be understood that the offset depends on the date in question, the Time Zone AND DST.
GetDate()-GetUTCDate only gives you the offset today at the server's TZ, which is not relevant.
I have seen only two working solution and I have search a lot.
1) A custom SQL function with a a couple of tables of base data such as Time Zones and DST rules per TZ.
Working but not very elegant. I can't post it since I don't own the code.
EDIT: Here is an example of this method
https://gist.github.com/drumsta/16b79cee6bc195cd89c8
2) Add a .net assembly to the db, .Net can do this very easily. This is working very well but the downside is that you need to configure several parameters on server level and the config is easily broken e.g. if you restore the database.
I use this method but I cant post it since I don't own the code.

This function will convert a UTC time to EST time with DST adjustment. You can change your designed time zone name in this function, or get it from registry:
Create Function fnConvertUTCTimetoESTTime(
#UTCTime as datetime
)
returns datetime
as
begin
return convert(datetime, convert(varchar(23), #UTCTime AT TIME ZONE 'UTC' AT TIME ZONE 'Eastern Standard Time', 121), 121)
end
go
select dbo.fnConvertUTCTimetoESTTime ('2020-3-8 5:00:00.000')
, dbo.fnConvertUTCTimetoESTTime ('2020-3-8 6:00:00.000')
, dbo.fnConvertUTCTimetoESTTime ('2020-3-8 7:00:00.000')
, dbo.fnConvertUTCTimetoESTTime ('2020-3-8 8:00:00.000')
--returns 0:00am, 1:00am, 3:00am, 4:00am
select dbo.fnConvertUTCTimetoESTTime ('2020-11-1 4:00:00.000')
, dbo.fnConvertUTCTimetoESTTime ('2020-11-1 5:00:00.000')
, dbo.fnConvertUTCTimetoESTTime ('2020-11-1 6:00:00.000')
, dbo.fnConvertUTCTimetoESTTime ('2020-11-1 7:00:00.000')
--returns 0:00am, 1:00am, 1:00am, 2:00am
Note you can not just return "#UTCTime AT TIME ZONE 'UTC' AT TIME ZONE 'Eastern Standard Time'" as the result because this result is actually a UTC time in EST format (when you compare this "fake" EST time or include it in an order clause it will be converted back to a UTC time).

The easiest answer is not always at the bottom, but this time it is, and can be seen already somewhere hidden in above comments.
Take your own 'AT TIME ZONE' to capture the TzOffset for your column/data field, and not the current SYSDATETIME.
In below data, 2 queries, one on feb data (DST is off, winter in Amsterdam) +1 diff
and 2nd query on april data in Amsterdam, so +2 hour diff.
select top 2 month(receiveTimeUTC) as MonthInWinterOrSpring
, receiveTimeUTC
, CONVERT(datetime, SWITCHOFFSET(CONVERT(datetimeoffset, receiveTimeUTC), DATENAME(TzOffset, SYSDATETIMEOFFSET()))) as LocalTimeWrongNoDST
, CONVERT(datetime, SWITCHOFFSET(CONVERT(datetimeoffset, receiveTimeUTC), DATENAME(TzOffset, receiveTimeUTC AT TIME ZONE 'Central European Standard Time' ))) as LocalTimeWithDST
from sensordetails order by id
select top 2 month(receiveTimeUTC) as MonthInWinterOrSpring, receiveTimeUTC
, CONVERT(datetime, SWITCHOFFSET(CONVERT(datetimeoffset, receiveTimeUTC), DATENAME(TzOffset, SYSDATETIMEOFFSET()))) as LocalTimeWrongNoDST
, CONVERT(datetime, SWITCHOFFSET(CONVERT(datetimeoffset, receiveTimeUTC), DATENAME(TzOffset, receiveTimeUTC AT TIME ZONE 'Central European Standard Time' ))) as LocalTimeWithDST
from sensordetails order by id desc
Results:
So this is a T-SQL (SQL Server Answer), no need for storedproc of functions.

For Azure SQL and ##Version >= SQL Server 2016 users, Below is a simple function using AT TIME ZONE.
CREATE FUNCTION [dbo].[Global_Convert_UTCTimeTo_LocalTime]
(
#LocalTimeZone VARCHAR(50),
#UTCDateTime DATETIME
)
RETURNS DATETIME
AS
BEGIN
DECLARE #ConvertedDateTime DATETIME;
SELECT #ConvertedDateTime = #UTCDateTime AT TIME ZONE 'UTC' AT TIME ZONE #LocalTimeZone
RETURN #ConvertedDateTime
END
GO
For types of values that #LocalTimeZone can take, please go to this link or Go to KEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones

Here's a version that accounts for daylight savings, UTC offset, and is not locked into a particular year.
---------------------------------------------------------------------------------------------------
--Name: udfToLocalTime.sql
--Purpose: To convert UTC to local US time accounting for DST
--Author: Patrick Slesicki
--Date: 3/25/2014
--Notes: Works on SQL Server 2008R2 and later, maybe SQL Server 2008 as well.
-- Good only for US States observing the Energy Policy Act of 2005.
-- Function doesn't apply for years prior to 2007.
-- Function assumes that the 1st day of the week is Sunday.
--Tests:
-- SELECT dbo.udfToLocalTime('2014-03-09 9:00', DEFAULT)
-- SELECT dbo.udfToLocalTime('2014-03-09 10:00', DEFAULT)
-- SELECT dbo.udfToLocalTime('2014-11-02 8:00', DEFAULT)
-- SELECT dbo.udfToLocalTime('2014-11-02 9:00', DEFAULT)
---------------------------------------------------------------------------------------------------
ALTER FUNCTION udfToLocalTime
(
#UtcDateTime AS DATETIME
,#UtcOffset AS INT = -8 --PST
)
RETURNS DATETIME
AS
BEGIN
DECLARE
#PstDateTime AS DATETIME
,#Year AS CHAR(4)
,#DstStart AS DATETIME
,#DstEnd AS DATETIME
,#Mar1 AS DATETIME
,#Nov1 AS DATETIME
,#MarTime AS TIME
,#NovTime AS TIME
,#Mar1Day AS INT
,#Nov1Day AS INT
,#MarDiff AS INT
,#NovDiff AS INT
SELECT
#Year = YEAR(#UtcDateTime)
,#MarTime = CONVERT(TIME, DATEADD(HOUR, -#UtcOffset, '1900-01-01 02:00'))
,#NovTime = CONVERT(TIME, DATEADD(HOUR, -#UtcOffset - 1, '1900-01-01 02:00'))
,#Mar1 = CONVERT(CHAR(16), #Year + '-03-01 ' + CONVERT(CHAR(5), #MarTime), 126)
,#Nov1 = CONVERT(CHAR(16), #Year + '-11-01 ' + CONVERT(CHAR(5), #NovTime), 126)
,#Mar1Day = DATEPART(WEEKDAY, #Mar1)
,#Nov1Day = DATEPART(WEEKDAY, #Nov1)
--Get number of days between Mar 1 and DST start date
IF #Mar1Day = 1 SET #MarDiff = 7
ELSE SET #MarDiff = 15 - #Mar1Day
--Get number of days between Nov 1 and DST end date
IF #Nov1Day = 1 SET #NovDiff = 0
ELSE SET #NovDiff = 8 - #Nov1Day
--Get DST start and end dates
SELECT
#DstStart = DATEADD(DAY, #MarDiff, #Mar1)
,#DstEnd = DATEADD(DAY, #NovDiff, #Nov1)
--Change UTC offset if #UtcDateTime is in DST Range
IF #UtcDateTime >= #DstStart AND #UtcDateTime < #DstEnd SET #UtcOffset = #UtcOffset + 1
--Get Conversion
SET #PstDateTime = DATEADD(HOUR, #UtcOffset, #UtcDateTime)
RETURN #PstDateTime
END
GO

I found the one off function way to be too slow when there is a lot of data. So I did it through joining to a table function that would allow for a calculation of the hour diff. It is basically datetime segments with the hour offset. A year would be 4 rows. So the table function
dbo.fn_getTimeZoneOffsets('3/1/2007 7:00am', '11/5/2007 9:00am', 'EPT')
would return this table:
startTime endTime offset isHr2
3/1/07 7:00 3/11/07 6:59 -5 0
3/11/07 7:00 11/4/07 6:59 -4 0
11/4/07 7:00 11/4/07 7:59 -5 1
11/4/07 8:00 11/5/07 9:00 -5 0
It does account for daylight savings. A sample of how it is uses is below and the full blog post is here.
select mt.startTime as startUTC,
dateadd(hh, tzStart.offset, mt.startTime) as startLocal,
tzStart.isHr2
from MyTable mt
inner join dbo.fn_getTimeZoneOffsets(#startViewUTC, #endViewUTC, #timeZone) tzStart
on mt.startTime between tzStart.startTime and tzStart.endTime

declare #mydate2 datetime
set #mydate2=Getdate()
select #mydate2 as mydate,
dateadd(minute, datediff(minute,getdate(),#mydate2),getutcdate())

In postgres this works very nicely..Tell the server the time at which the time is saved, 'utc', and then ask it to convert to a specific timezone, in this case 'Brazil/East'
quiz_step_progresses.created_at at time zone 'utc' at time zone 'Brazil/East'
Get a complete list of timezones with the following select;
select * from pg_timezone_names;
See details here.
https://popsql.com/learn-sql/postgresql/how-to-convert-utc-to-local-time-zone-in-postgresql

Ron's answer contains an error. It uses 2:00 AM local time where the UTC equivalent is required. I don't have enough reputation points to comment on Ron's answer so a corrected version appears below:
-- =============================================
-- Author: Ron Smith
-- Create date: 2013-10-23
-- Description: Converts UTC to DST
-- based on passed Standard offset
-- =============================================
CREATE FUNCTION [dbo].[fn_UTC_to_DST]
(
#UTC datetime,
#StandardOffset int
)
RETURNS datetime
AS
BEGIN
declare
#DST datetime,
#SSM datetime, -- Second Sunday in March
#FSN datetime -- First Sunday in November
-- get DST Range
set #SSM = datename(year,#UTC) + '0314'
set #SSM = dateadd(hour,2 - #StandardOffset,dateadd(day,datepart(dw,#SSM)*-1+1,#SSM))
set #FSN = datename(year,#UTC) + '1107'
set #FSN = dateadd(second,-1,dateadd(hour,2 - (#StandardOffset + 1),dateadd(day,datepart(dw,#FSN)*-1+1,#FSN)))
-- add an hour to #StandardOffset if #UTC is in DST range
if #UTC between #SSM and #FSN
set #StandardOffset = #StandardOffset + 1
-- convert to DST
set #DST = dateadd(hour,#StandardOffset,#UTC)
-- return converted datetime
return #DST
END

The UNIX timestamp is merely the number of seconds between a particular date and the Unix Epoch,
SELECT DATEDIFF(SECOND,{d '1970-01-01'},GETDATE()) // This Will Return the UNIX timestamp In SQL server
you can create a function for local date time to Unix UTC conversion using Country Offset
Function to Unix Time Stamp In SQL server

It's simple. Try this for Azure SQL Server:
SELECT YourDateTimeColumn AT TIME ZONE 'Eastern Standard Time' FROM YourTable
For Local SQL Server :
SELECT CONVERT(datetime2, SWITCHOFFSET(CONVERT(datetimeoffset, gETDATE()), DATENAME(TzOffset, gETDATE() AT TIME ZONE 'Eastern Standard Time'))) FROM YourTable

For anyone still trying to solve this issue, here's a proof of concept that works in SQL Server 2017
declare
#StartDate date = '2020-01-01'
;with cte_utc as
(
select
1 as i
,CONVERT(datetime, #StartDate) AS UTC
,datepart(weekday, CONVERT(datetime, #StartDate)) as Weekday
,datepart(month, CONVERT(datetime, #StartDate)) as [Month]
,datepart(YEAR, CONVERT(datetime, #StartDate)) as [Year]
union all
Select
i + 1
,dateadd(d, 1, utc)
,datepart(weekday, CONVERT(datetime, dateadd(d, 1, utc))) as Weekday
,datepart(month, CONVERT(datetime, dateadd(d, 1, utc))) as [Month]
,datepart(YEAR, CONVERT(datetime, dateadd(d, 1, utc))) as [Year]
from
cte_utc
where
(i + 1) < 32767
), cte_utc_dates as
(
select
*,
DENSE_RANK()OVER(PARTITION BY [Year], [Month], [Weekday] ORDER BY Utc) WeekDayIndex
from
cte_utc
), cte_hours as (
select 0 as [Hour]
union all
select [Hour] + 1 from cte_hours where [Hour] < 23
)
select
d.*
, DATEADD(hour, h.Hour, d.UTC) AS UtcTime
,CONVERT(datetime, DATEADD(hour, h.Hour, d.UTC) AT TIME ZONE 'UTC' AT TIME ZONE 'Central Standard Time') CST
,CONVERT(datetime, DATEADD(hour, h.Hour, d.UTC) AT TIME ZONE 'UTC' AT TIME ZONE 'Eastern Standard Time') EST
from
cte_utc_dates d, cte_hours h
where
([Month] = 3 and [Weekday] = 1 and WeekDayIndex = 2 )-- dst start
or
([Month] = 11 and [Weekday] = 1 and WeekDayIndex = 1 )-- dst end
order by
utc
OPTION (MAXRECURSION 32767)
GO

As a warning - if you're going to use the following (note the milliseconds instead of minutes):
SELECT DATEADD(ms, DATEDIFF(ms, GETUTCDATE(), GETDATE()), MyTable.UtcColumn)
AS ColumnInLocalTime
FROM MyTable
Keep in mind that the DATEDIFF part will not always return the same number. So don't use it to compare DateTimes down to milliseconds.

This should be able to get server time with DST
declare #dt datetime
set #dt = getutcdate() -- GMT equivalent
sysdatetimeoffset takes DST into account
select [InputTime] = #dt
, [LocalTime2] = dateadd(mi, datediff(mi, sysdatetimeoffset(),getdate()), #dt)

First function: configured for italian time zone (+1, +2), switch dates: last sunday of march and october, return the difference between the current time zone and the datetime as parameter.
Returns:
current timezone < parameter timezone ==> +1
current timezone > parameter timezone ==> -1
else 0
The code is:
CREATE FUNCTION [dbo].[UF_ADJUST_OFFSET]
(
#dt_utc datetime2(7)
)
RETURNS INT
AS
BEGIN
declare #month int,
#year int,
#current_offset int,
#offset_since int,
#offset int,
#yearmonth varchar(8),
#changeoffsetdate datetime2(7)
declare #lastweek table(giorno datetime2(7))
select #current_offset = DATEDIFF(hh, GETUTCDATE(), GETDATE())
select #month = datepart(month, #dt_utc)
if #month < 3 or #month > 10 Begin Set #offset_since = 1 Goto JMP End
if #month > 3 and #month < 10 Begin Set #offset_since = 2 Goto JMP End
--If i'm here is march or october
select #year = datepart(yyyy, #dt_utc)
if #month = 3
Begin
Set #yearmonth = cast(#year as varchar) + '-03-'
Insert Into #lastweek Values(#yearmonth + '31 03:00:00.000000'),(#yearmonth + '30 03:00:00.000000'),(#yearmonth + '29 03:00:00.000000'),(#yearmonth + '28 03:00:00.000000'),
(#yearmonth + '27 03:00:00.000000'),(#yearmonth + '26 03:00:00.000000'),(#yearmonth + '25 03:00:00.000000')
--Last week of march
Select #changeoffsetdate = giorno From #lastweek Where datepart(weekday, giorno) = 1
if #dt_utc < #changeoffsetdate
Begin
Set #offset_since = 1
End Else Begin
Set #offset_since = 2
End
End
if #month = 10
Begin
Set #yearmonth = cast(#year as varchar) + '-10-'
Insert Into #lastweek Values(#yearmonth + '31 03:00:00.000000'),(#yearmonth + '30 03:00:00.000000'),(#yearmonth + '29 03:00:00.000000'),(#yearmonth + '28 03:00:00.000000'),
(#yearmonth + '27 03:00:00.000000'),(#yearmonth + '26 03:00:00.000000'),(#yearmonth + '25 03:00:00.000000')
--Last week of october
Select #changeoffsetdate = giorno From #lastweek Where datepart(weekday, giorno) = 1
if #dt_utc > #changeoffsetdate
Begin
Set #offset_since = 1
End Else Begin
Set #offset_since = 2
End
End
JMP:
if #current_offset < #offset_since Begin
Set #offset = 1
End Else if #current_offset > #offset_since Set #offset = -1 Else Set #offset = 0
Return #offset
END
Then the function that convert date
CREATE FUNCTION [dbo].[UF_CONVERT]
(
#dt_utc datetime2(7)
)
RETURNS datetime
AS
BEGIN
declare #offset int
Select #offset = dbo.UF_ADJUST_OFFSET(#dt_utc)
if #dt_utc >= '9999-12-31 22:59:59.9999999'
set #dt_utc = '9999-12-31 23:59:59.9999999'
Else
set #dt_utc = (SELECT DATEADD(mi, DATEDIFF(mi, GETUTCDATE(), GETDATE()), #dt_utc) )
if #offset <> 0
Set #dt_utc = dateadd(hh, #offset, #dt_utc)
RETURN #dt_utc
END

-- get indian standard time from utc
CREATE FUNCTION dbo.getISTTime
(
#UTCDate datetime
)
RETURNS datetime
AS
BEGIN
RETURN dateadd(minute,330,#UTCDate)
END
GO

You have to reformat the string as well as converting to the correct time. In this case I needed Zulu time.
Declare #Date datetime;
Declare #DateString varchar(50);
set #Date = GETDATE();
declare #ZuluTime datetime;
Declare #DateFrom varchar (50);
Declare #DateTo varchar (50);
set #ZuluTime = DATEADD(second, DATEDIFF(second, GETDATE(), GETUTCDATE()), #Date);
set #DateString = FORMAT(#ZuluTime, 'yyyy-MM-ddThh:mm:ssZ', 'en-US' )
select #DateString;

Best way for Oracle:
With hardcoded datetime:
SELECT TO_CHAR(CAST((FROM_TZ(CAST(TO_DATE('2018-10-27 21:00', 'YYYY-MM-DD HH24:MI') AS TIMESTAMP), 'UTC') AT TIME ZONE 'EET') AS DATE), 'YYYY-MM-DD HH24:MI') UTC_TO_EET FROM DUAL
Result:
2018-10-28 00:00
With column and table names:
SELECT TO_CHAR(CAST((FROM_TZ(CAST(COLUMN_NAME AS TIMESTAMP), 'UTC') AT TIME ZONE 'EET') AS DATE), 'YYYY-MM-DD HH24:MI') UTC_TO_EET FROM TABLE_NAME

I have code to perform UTC to Local and Local to UTC times which allows conversion using code like this
DECLARE #usersTimezone VARCHAR(32)='Europe/London'
DECLARE #utcDT DATETIME=GetUTCDate()
DECLARE #userDT DATETIME=[dbo].[funcUTCtoLocal](#utcDT, #usersTimezone)
and
DECLARE #usersTimezone VARCHAR(32)='Europe/London'
DECLARE #userDT DATETIME=GetDate()
DECLARE #utcDT DATETIME=[dbo].[funcLocaltoUTC](#userDT, #usersTimezone)
The functions can support all or a subset of timezones in the IANA/TZDB as provided by NodaTime - see the full list at https://nodatime.org/TimeZones
Be aware that my use case means I only need a 'current' window, allowing the conversion of times within the range of about +/- 5 years from now. This means that the method I've used probably isn't suitable for you if you need a very wide period of time, due to the way it generates code for each timezone interval in a given date range.
The project is on GitHub: https://github.com/elliveny/SQLServerTimeConversion
This generates SQL function code as per this example

I used switchoffset to convert from utc time to local time. The time zone offset can be determined by using datename(tzoffset,systemdatetimeoffset()). Likewise if you want to get the elapsed time then use getutcdate keeping the time in utc time for the datediff function.
select
,[Field1]
,Format(SWITCHOFFSET([MyDateOnUTC],DATENAME(TZOFFSET, SYSDATETIMEOFFSET())),'MM/dd/yyyy hh:mm:ss tt') UtcToLocalTime
,datediff(minute,[ClaimedOnUTC],getutcdate()) ElapsedMinutes
from dbo.my_table

Here's a simpler one that takes dst in to account
CREATE FUNCTION [dbo].[UtcToLocal]
(
#p_utcDatetime DATETIME
)
RETURNS DATETIME
AS
BEGIN
RETURN DATEADD(MINUTE, DATEDIFF(MINUTE, GETUTCDATE(), #p_utcDatetime), GETDATE())
END

I've found that this function is faster than other solutions using a separate table or loops. It's just a basic case statement. Given that all months between April and October have a -4-hour offset (Eastern Time) we just need to add a few more case lines for the fringe days. Otherwise, the offset is -5 hours.
This is specific to a conversion from UTC to Eastern time, but additional time zone functions can be added as needed.
USE [YourDatabaseName]
GO
/****** Object: UserDefinedFunction [dbo].[ConvertUTCtoEastern] Script Date: 11/2/2016 5:21:52 PM ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE FUNCTION [dbo].[ConvertUTCtoEastern]
(
#dtStartDate DATETIME
)
RETURNS DATETIME
AS
BEGIN
DECLARE #Working DATETIME
DECLARE #Returned DATETIME
SET #Working = #dtStartDate
SET #Working =
case when month(#Working) between 4 and 10 then dateadd(HH,-4,#Working)
when #Working between '2017-03-12' and '2017-11-05' then dateadd(HH,-4,#Working)
when #Working between '2016-03-13' and '2016-11-06' then dateadd(HH,-4,#Working)
when #Working between '2015-03-08' and '2015-11-01' then dateadd(HH,-4,#Working)
when #Working between '2014-03-09' and '2014-11-02' then dateadd(HH,-4,#Working)
when #Working between '2013-03-10' and '2013-11-03' then dateadd(HH,-4,#Working)
when #Working between '2012-03-11' and '2012-11-04' then dateadd(HH,-4,#Working)
else dateadd(HH,-5,#Working) end
SET #Returned = #Working
RETURN #Returned
END
GO

TSQL strip date from datetime

What is the best way to strip the date from a DATETIME so only time is left to do a comparison?
I know I can do the following:
CONVERT(DATETIME, CONVERT(VARCHAR(8), GETDATE(),8))
But this involves convert and characters. If I wanted to check whether a time (including minutes) was between two other times stored in DATETIME columns, is there an elegant way to do this without having to rely on converting to character strings?

If you're using SQL 2008
SELECT CAST(GETDATE() AS TIME)

Try the TimeOnly function from Essential SQL Server Date, Time, and DateTime Functions:
create function TimeOnly(#DateTime DateTime)
returns datetime
as
begin
return dateadd(day, -datediff(day, 0, #datetime), #datetime)
end
go
Or simply cast the DateTime as Time in SQL Server 2008:
declare #time as time
set #time = cast(dateTimeVal as time)

DECLARE
#Now DateTime,
#Today DateTime,
#Time DateTime
SET #Now = GetDate()
SET #Today = DateAdd(dd, DateDiff(dd, 0, #Now), 0)
SET #Time = DateAdd(ss, DateDiff(ss, #Today, #Now), 0)
SELECT #Time

Just another way to get date and time from datetime.
datetime in SQL Server implemented as float value where whole part floor(value) is day from 1900-01-01 and fractional part (value - floor(value)) is part of twenty-four hours elapsed from start of day
select
d as [datetime],
cast(cast(T.d as float) - floor(cast(T.d as float)) as datetime) as [time],
cast(floor(cast(T.d as float)) as datetime) as [date]
from
(values
(getdate()),
('1753-01-01 23:59:59.700'),
('1899-12-31 00:00:00.300'),
('1900-01-01 00:00:00.300')
) as T(d);