MySql: IST and Hours Sinse Insertion

# IST: Indian Standerd Time , Assuem server time UST
# hours_since: time in Hours wince record insertion

CREATE TABLE `tbl` (
`id` int(10) unsigned NOT NULL auto_increment,
`dt` timestamp NOT NULL default '0000-00-00 00:00:00',
PRIMARY KEY (`id`)
)

insert into tbl (dt ) values
( '2008-01-01' ), ( '2008-01-01' ), ( '2008-01-01' ), ( '2008-01-01' ), ( '2008-01-01' ), ( '2008-01-01' ),
( '2008-01-01' ), ( '2008-01-01' ), ( '2008-01-01' ), ( '2008-01-01' ), ( '2008-01-01' ), ( '2008-01-01' ),
( '2008-01-01' ), ( '2008-01-01' ), ( '2008-01-01' ), ( '2008-01-01' ), ( '2008-01-01' ), ( '2008-01-01' );

update tbl set dt = date_add( now(), interval ( 0 - ( 3 * id) ) hour ) ;

select
timediff( now(), dt ),
date_add( dt, INTERVAL 90 minute) ,
now(),
dt
from tbl;

select
time_format( timediff( now(), dt ), '%H:%i:%s') as `hours_since`,
date_format( date_add( dt, INTERVAL 90 minute), '%d-%b-%Y') as `IST` ,
now(),
dt
from tbl;