There's a code- *#92702689#
On entering this code, it displays -
1.Serial Number,
2.Date Made,
3.Purchase Date,
4.Date of last repair (0000 for no repairs),
5.Transfer User Data.
To exit this mode you may need to switch your phone off then on again.
Or else it may simply display 'Life Timer' . Life Timer is the amount of time the phone has been used for making / receiving calls. So, if you've bought a new phone, the life timer should be set to zero.
for Sony Ericsson, press the key R*LL*L* where R and L is the right n left navigation buttons.
*credit to awe_ploon
