SQL Server datetime to bigint (epoch) overflow

Question

I have a 'datetime' column with value 2013-03-22 15:19:02.000

I need to convert this value into epoch time and store it in a 'bigint' field

The actual epoch value for the above time is, 1363945741898, when I use

  select DATEDIFF(s, '1970-01-01 00:00:00', '2013-03-22 15:19:02.000')

I get, 1363965542, when I use

select DATEDIFF(ms, '1970-01-01 00:00:00', '2013-03-22 15:19:02.000')

I get,

Msg 535, Level 16, State 0, Line 1 The datediff function resulted in an overflow. The number of dateparts separating two date/time instances is too large. Try to use datediff with a less precise datepart.

How to get the exact epoch value from the 'datetime' field

I use SQL Server 2008. Also this should work with 2005.

Answer 1

Here is an example, not tested, written from free hand :)

declare @v_Date datetime
set @v_Date = '2013-03-22 15:19:02.000'

declare @v_DiffInSeconds integer
declare @v_DiffInMSeconds bigint

select @v_DiffInSeconds = DATEDIFF(s, '1970-01-01 00:00:00', @v_Date)
select @v_DiffInMSeconds = cast(@v_DiffInSeconds as bigint) * 1000 + cast(DATEPART(ms, @v_Date) as bigint)

Edit I have made this example below to illustrate the time zone conversion. The given time stamp (in seconds where I have removed the last three digits "898") is here converted to the local IST time zone by adding the 5.5 hours (19800 seconds) and I convert it back to the time stamp from local time to GMT again. Below calculations matches the values in the question (in seconds).

declare @v_time datetime
set @v_time = '1970-01-01 00:00:00'

declare @v_date datetime
set @v_date = '2013-03-22 15:19:01'

-- This returns "March, 22 2013 15:19:01"
select dateadd(s, (1363945741 + 19800), @v_time)

-- This returns "1363945741"
select datediff(s, @v_time, @v_date) - 19800

Answer 2

When tried to get exact milliseconds we get the overflow exception. we can get the values till seconds and multiply with 1000.

This is equivalent to new Date().getTime() in javascript:

Use the below statement to get the time in seconds.

SELECT cast(DATEDIFF(s, '1970-01-01 00:00:00.000', '2016-12-09 16:22:17.897' ) as bigint)

Use the below statement to get the time in milliseconds.

SELECT cast(DATEDIFF(s, '1970-01-01 00:00:00.000', '2016-12-09 16:22:17.897' ) as bigint) * 1000

convert epoch to human readable date time using below statement:

select DATEADD(s, 1481300537, '1970-01-01 00:00:00')

Answer 3

Epoch to datetime

create function [dbo].[EpochToDate](@Date bigint)
returns datetime
begin
    return (select dateadd(s, @Date, '19700101'))
end 

Answer 4

Use below code to get human readable date from epoch time

select DATEADD(s,convert(bigint,@date)/2, DATEADD(s, convert(bigint,@date)/2, '1970-01-01 00:00:00'))