RMAN change backupset until time

 RMAN> change backupset 77,78,79 keep until time 'sysdate + 40';

allocated channel: ORA_DISK_1

channel ORA_DISK_1: SID=74 device type=DISK

keep attributes for the backup are changed

backup will be obsolete on date 09-JAN-21

backup set key=77 RECID=77 STAMP=1057863668

keep attributes for the backup are changed

backup will be obsolete on date 09-JAN-21

backup set key=78 RECID=78 STAMP=1057863673

keep attributes for the backup are changed

backup will be obsolete on date 09-JAN-21

backup set key=79 RECID=79 STAMP=1057863674

RMAN>