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.

2

30 Answers

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

17

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')))

7

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.

6

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

2

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.

0

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

3

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

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).

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

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.

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

2

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

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.

1

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.

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

2

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

1

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

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:

This generates SQL function code as per this example

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

1

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

1

This can be done without a function. Code below will convert a UTC time to Mountain time accounting for daylight savings. Adjust all the -6 and -7 numbers to your timezone accordingly (i.e. for EST you would adjust to -4 and -5 respectively)

--Adjust a UTC value, in the example the UTC field is identified as UTC.Field, to account for daylight savings time when converting out of UTC to Mountain time.
CASE --When it's between March and November, it is summer time which is -6 from UTC WHEN MONTH ( UTC.Field ) > 3 AND MONTH ( UTC.Field ) < 11 THEN DATEADD ( HOUR , -6 , UTC.Field ) --When its March and the day is greater than the 14, you know it's summer (-6) WHEN MONTH ( UTC.Field ) = 3 AND DATEPART ( DAY , UTC.Field ) >= 14 THEN --However, if UTC is before 9am on that Sunday, then it's before 2am Mountain which means it's still Winter daylight time. CASE WHEN DATEPART ( WEEKDAY , UTC.Field ) = 1 AND UTC.Field < '9:00' --Before 2am mountain time so it's winter, -7 hours for Winter daylight time THEN DATEADD ( HOUR , -7 , UTC.Field ) --Otherwise -6 because it'll be after 2am making it Summer daylight time ELSE DATEADD ( HOUR , -6 , UTC.Field ) END WHEN MONTH ( UTC.Field ) = 3 AND ( DATEPART ( WEEKDAY , UTC.Field ) + 7 ) <= DATEPART ( day , UTC.Field ) THEN --According to the date, it's moved onto Summer daylight, but we need to account for the hours leading up to 2am if it's Sunday CASE WHEN DATEPART ( WEEKDAY , UTC.Field ) = 1 AND UTC.Field < '9:00' --Before 9am UTC is before 2am Mountain so it's winter Daylight, -7 hours THEN DATEADD ( HOUR , -7 , UTC.Field ) --Otherwise, it's summer daylight, -6 hours ELSE DATEADD ( HOUR , -6 , UTC.Field ) END --When it's November and the weekday is greater than the calendar date, it's still Summer so -6 from the time WHEN MONTH ( UTC.Field ) = 11 AND DATEPART ( WEEKDAY , UTC.Field ) > DATEPART ( DAY , UTC.Field ) THEN DATEADD ( HOUR , -6 , UTC.Field ) WHEN MONTH ( UTC.Field ) = 11 AND DATEPART ( WEEKDAY , UTC.Field ) <= DATEPART ( DAY , UTC.Field ) --If the weekday is less than or equal to the calendar day it's Winter daylight but we need to account for the hours leading up to 2am. CASE WHEN DATEPART ( WEEKDAY , UTC.Field ) = 1 AND UTC.Field < '8:00' --If it's before 8am UTC and it's Sunday in the logic outlined, then it's still Summer daylight, -6 hours THEN DATEADD ( HOUR , -6 , UTC.Field ) --Otherwise, adjust for Winter daylight at -7 ELSE DATEADD ( HOUR , -7 , UTC.Field ) END --If the date doesn't fall into any of the above logic, it's Winter daylight, -7 ELSE DATEADD ( HOUR , -7 , UTC.Field )
END

1

Your Answer

Sign up or log in

Sign up using Google Sign up using Facebook Sign up using Email and Password Submit

Post as a guest

Post Your Answer Discard

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy