declare @jsondate varchar(40) = '\/Date(1328029200000+0700)\/';
select substring(@jsondate,8,10) -- seconds
,substring(@jsondate,18,3) -- milliseconds
,substring(@jsondate,21,5) -- utc offset
,
-- this next expression is what you need
cast(convert(char(20),
dateadd(ms,1*substring(@jsondate,18,3),
dateadd(ss,1*substring(@jsondate,8,10),'19700101'))
,120) + stuff(substring(@jsondate,21,5),4,0,':')
as datetimeoffset(4));
-- result 2012-01-31 17:00:00.0000 +07:00
