Because of the time is correctly saved
We understand that your Ds1307 is work properly
and your write and read routines are correct

venu wrote:
it just holds the last value and increments furthur
Do the time is incrementing only 1 second ?

if not:
the problem is in your source code or wiring configuration.
at first
for initializing ds1307 you must setb MSB in address 7 (control register)

else
the error is in your crystal,
and you must review the xtal pins and crystal accuracy.