Convert Datetime column from UTC to local time in select statement

Question

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.