SQL Server - converting 13 digit numeric to datetime

Question

How can I convert a 13 digit numeric like 1314637182953 to datetime in SQL Server? Both casting and converting directly give an arithmetic overflow error!

Same result with the query below:

select Convert(datetime, cast(START_DATE as varchar(8)), 112), * 
from table

Answer 1

Assuming it's UNIX time in milliseconds, try this:

DATEADD(SECOND, START_DATE/1000 ,'1970/1/1')

For the number from your post, SQL-2008 returns 2011-08-29 16:59:42.000