List expiration dates of Oracle backups
Oracle, in contrast with the name, can not predict the future.

If you have a retention policy configured as recovery window of 14 days or redundancy 2, the database does not know when your next full backup will succeed. Just because you have a full backup scheduled on every Saturady, that does not necessarily mean that backup will succeed and old backups can be deleted after that point of time.

Backups do not have an expiration date, unless you mean backups created with the KEEP option. For a backup created with the KEEP option, the database does list the time until it will be kept:

list backup;

BS Key  Type LV Size       Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ -------------------
7       Full    211.59M    DISK        00:00:18     2016-04-04 21:50:15
        BP Key: 7   Status: AVAILABLE  Compressed: YES  Tag: TAG20160404T214957
        Piece Name: /nasdata/exdb/0dr27io5_1_1
        Keep: BACKUP_LOGS        Until: 2017-04-04 21:49:57
  List of Datafiles in backup set 7
  File LV Type Ckp SCN    Ckp Time            Name
  ---- -- ---- ---------- ------------------- ----
  1       Full 38380954   2016-04-04 21:49:57 /oradata/exdb/system01.dbf
  2       Full 38380954   2016-04-04 21:49:57 /oradata/exdb/myxml01.dbf
  6       Full 38380954   2016-04-04 21:49:57 /oradata/exdb/users01.dbf
  9       Full 38380954   2016-04-04 21:49:57 /oradata/exdb/ut2.dbf

...


Notice the line:

        Keep: BACKUP_LOGS        Until: 2017-04-04 21:49:57


I created this backup with the keep until time 'sysdate+365' option.