still it did not updated frnd,

$ dt=`date -u +%d-%m-%y`
$
$ echo $dt
29-01-08
$
$ cat tst.txt
Date 12-01-08
$
$ awk -v dat=$dt '{if( $1 ~ /Date/) print $1" "dat;}' tst.txt
Date 29-01-08
$
$
$ cat tst.txt
Date 12-01-08
$