If you want to change the expiration date on data images on tapes in NetBackup, the functionality in the gui in useless. You can use the bpexpdate command on the commandline. To use it, start a cmd box as administrator:

To change a date on a media with media id O731L4:

C:\Windows\system32>bpexpdate -m O731L4 -d 09/12/2011
Are you SURE you want to change O731L4
to expire on        12-9-2011 0:00:00 y/n (n)? y

To change a date and time on a media with media id O731L4:

C:\Windows\system32>bpexpdate -m O731L4 -d 09/12/2011 03:00:00
Are you SURE you want to change O731L4
to expire on        12-9-2011 3:00:00 y/n (n)? y

To never expire the media:

C:\Windows\system32>bpexpdate -m O731L4 -d infinity
Are you SURE you want to change O731L4
to NEVER expire y/n (n)? y

To immediately expire the media:

C:\Windows\system32>bpexpdate -m O706L4 -d 0
Media O706L4 is due to expire at 07/13/2011 03:02:32
Are you sure that the data on this media is not critical to
your business, and you are sure you want to delete O706L4 y/n (n)? y

You can also change the expiration time based on the backup id. To find the specific backup id do a search in the catalog and note the backup id (and the copy number) from the search results. Then perform the correct command:

C:\Windows\system32>bpexpdate -backupid server_1335546010 -d 05/27/2012
Are you SURE you want to change server_1335546010
to expire on    5/27/2012 12:00:00 AM y/n (n)? y
requested media id is not assigned to this host in the EMM database

As you see you can get an error regarding the media not being assigned to the host. When a backup has multiple copies you should also submit the copy number of the backup id you want to change the expriration date from:

C:\Windows\system32>bpexpdate -backupid server_1335546010 -d 05/27/2012 -copy 1
Are you SURE you want to change server_1335546010 copy 1
to expire on    5/27/2012 12:00:00 AM y/n (n)? y