The HMC date and time in format: MMDDhhmm[[CC]YY][.ss]

chhmc -c date -s modify –datetime 09121621

Example:-

# chhmc -c date -s modify –datetime 09121621
The Customize Date/Time request completed successfully. Please reboot the HMC.

# date
Fri Sep 12 16:21:03 UTC 2014