Convert date in millisecond to date - sql-server

Question

In my table, I have a column that contains date in millisecond like this:
table a
dateinmili
1440301846096 //first six month date
1443589721039 //second six month date
I use that for my Android device and it works fine. When I want to use this time in a PROCEDURE in SQL Server and convert this time to human time (understandable for human) and date I have a problem.
I'm in Iran which uses UTC time in first six Persian date month 4.30 and 3.30 in second six month.
For convert date in PROCEDURE I use this code:
CONVERT(nVARCHAR(10),DATEADD(mi, DATEDIFF(mi, GETUTCDATE(), GETDATE()), DATEADD(ss,dateinmili/1000,'1970-01-01')),8) as date
DATEADD(mi, DATEDIFF(mi, GETUTCDATE(), GETDATE()), DATEADD(ss,dateinmili/1000,'1970-01-01')) as time
and here is my problem:
When I convert date in second six month and date registered in first six month of year, I get 1 hour difference between real time and converted time. I know that is because
DATEDIFF(mi, GETUTCDATE(), GETDATE())
method which return different between UTC time and local time when ever its called (in my example return 3:30 not 4:30 ) but I don't know how can I fix that?
I can add column which contain current UTC time but I am looking for another way.
update
I see this question and it's not my problem convert long to date.
My problem is in my country UTC time is not constant in whole year and change between 3.30 and 4.30, for example I have date registered in first six month (Persian six month) like 1440271800000 and convert it now which we are in second six month (Persian six month) and use this code for convert.
declare #unixTS bigint
set #unixTS = 1440271800000
select dateadd(ms, #unixTS%(3600*24*1000),
dateadd(day, #unixTS/(3600*24*1000), '1970-01-01 03:30:00.0')
)
I get this
2015-08-22 23:00:00.000
but it's not right date; the right date is:
2015-08-23 00:00:00.000
because when time registered UTC was 4.30 and not 3.30 but know when I convert
it UTC is 3.30.
I wish if there was a method in SQL which return past UTC time different; I mean put a date to that and return that time different between local time and gmt time my problem solved.
I hope you understand my problem.

Answer 1

In the US we have Daylight Savings Time in the summer, in most areas that means that we are also not fixed offset from UTC. Older versions of MS Dynamics CRM used to save everything in UTC, so when we wanted to export data in local time, we had a similar exercise. I created a set of SQL functions that would take the standard GMT offset and the datetime to I wanted to convert and figure out whether to apply the standard or DST offset and return the local datetime. If your offset follows a set of rules, then you can modify this:
CREATE function [dbo].[DC_GMTtoLocal]
(#OrigGMT datetime,
#StandardOffset int)
RETURNS datetime
AS
BEGIN
DECLARE #RevDate datetime
set #RevDate = CASE dbo.DC_DaylightSavingTime_IsInEffect(#OrigGMT)
WHEN 1 THEN DATEADD(hour, - #StandardOffset + 1, #OrigGMT) -- in DST
ELSE DATEADD(hour, - #StandardOffset, #OrigGMT) -- Not In DST
END
return #RevDate
END
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE function [dbo].[DC_DaylightSavingTime_IsInEffect]
(#DtTime datetime)
RETURNS tinyint
AS
BEGIN
DECLARE #DLSStart datetime
, #DLSEnd datetime
, #DLSActive tinyint
SET #DLSActive = 0
If DATEADD(YEAR,3,GETDATE()) > #DtTime
BEGIN
SET #DLSStart =(SELECT dbo.DC_GetDaylightSavingsTimeStart(CONVERT(varchar,DATEPART(YEAR,#DtTime))))
SET #DLSEnd =(SELECT dbo.DC_GetDaylightSavingsTimeEnd(CONVERT(varchar,DATEPART(YEAR,#DtTime))))
IF #DtTime BETWEEN #DLSStart AND #DLSEnd
BEGIN
SET #DLSActive = 1
END
--SET #DLSActive = 0
END
RETURN #DLSActive
END
GO
CREATE function [dbo].[DC_GetDaylightSavingsTimeStart]
(#Year varchar(4))
RETURNS smalldatetime
as
--Start date: We evaluate the day of the week corresponding to the first day of the month and find the second Sunday of March using a Case statement
begin
declare #DTSStartWeek smalldatetime, #DTSEndWeek smalldatetime
set #DTSStartWeek = '03/01/' + convert(varchar,#Year)
return case datepart(dw,#DTSStartWeek)
when 1 then
dateadd(hour,170,#DTSStartWeek)
when 2 then
dateadd(hour,314,#DTSStartWeek)
when 3 then
dateadd(hour,290,#DTSStartWeek)
when 4 then
dateadd(hour,266,#DTSStartWeek)
when 5 then
dateadd(hour,242,#DTSStartWeek)
when 6 then
dateadd(hour,218,#DTSStartWeek)
when 7 then
dateadd(hour,194,#DTSStartWeek)
end
end
GO
CREATE function [dbo].[DC_GetDaylightSavingsTimeEnd]
(#Year varchar(4))
RETURNS smalldatetime
as
-- End date: We evaluate the day of the week corresponding to the first day of the month and find the first Sunday of March using a Case statement
begin
declare #DTSEndWeek smalldatetime
set #DTSEndWeek = '11/01/' + convert(varchar,#Year)
return case datepart(dw,dateadd(week,1,#DTSEndWeek))
when 1 then
dateadd(hour,2,#DTSEndWeek)
when 2 then
dateadd(hour,146,#DTSEndWeek)
when 3 then
dateadd(hour,122,#DTSEndWeek)
when 4 then
dateadd(hour,98,#DTSEndWeek)
when 5 then
dateadd(hour,74,#DTSEndWeek)
when 6 then
dateadd(hour,50,#DTSEndWeek)
when 7 then
dateadd(hour,26,#DTSEndWeek)
end
end
GO