Show Datetime according to user Country

Question

i have data in local time (according to Pakistan standard time )
 
Like
--------- 
 
sno name Date_Time
 
1 abc 10-Jan-2012 4:29
2 abc 10-Jan-2012 6:29
 
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i have to show data of "Date_Time" according to user standard time 
suppose if any user login to India
 
it should show " Date_Time " according to their standard 
as Data Store In Database on " 10-Jan-2012 4:29 "
but there are half hour difference between Pakistan and 
India
 
so it should be showed 
" 10-Jan-2010 4:59 " for Indian User Instead of this " 10-Jan-2010 4:29"
as Pakistani User Login so it should show this
 
" 10-Jan-2010 4:29 " and so on for others user