RMAN may not display dates and times of backups the way that you want it. The format of the date time displayed is controlled by the environment variable NLS_DATE_FORMAT. Make sure it is set before invoking rman, for example:
export NLS_DATE_FORMAT=DD_MON_YYYY_HH24:MI:SS
rman target /
list backup;
…
BS Key Type LV Size Device Type Elapsed Time Completion Time
——- —- — ———- ———– ———— ——————–
16 Full 11.11M DISK 00:00:01 14_OCT_2017_13:07:20
BP Key: 16 Status: AVAILABLE Compressed: NO Tag: TAG20171014T130719
Piece Name: /u01/app/oracle/fast_recovery_area/GGTARGET/autobackup/2017_10_14/o1_mf_s_957359239_dy4k280o_.bkp
SPFILE Included: Modification time: 14_OCT_2017_12:59:54
SPFILE db_unique_name: GGTARGET
Control File Included: Ckp SCN: 13584253 Ckp time: 14_OCT_2017_13:07:19