This lists( Index of the files) from your backup ::
# frecover -I /tmp/index -f /dev/rmt/Xm
This can also work,Use the -V option:
# frecover -V /tmp/index01 -f /dev/rmt/Xm
Now u check for the required time and date in the file /tmp/index01 on 'time and date' field by grep or else.
Thanks,
Information is Wealth ; Knowledge is Power