/etc/profile or /etc/bashrc

HISTTIMEFORMAT='%F %T '
HISTSIZE=100000
HISTFILESIZE=100000
#always refresh
PROMPT_COMMAND='history -a; history -c; history -r'

$ HISTTIMEFORMAT="%Y/%m/%d %H:%M:%S "

 1000  2017/01/11 00:14:12 shutdown -h  now
 1001  2017/01/11 00:14:19 alias 
 1002  2017/01/11 00:14:29 unalias mv
 1003  2017/01/11 00:14:32 alias
 1004  2017/01/11 00:15:09 man unalias
 1005  2017/01/11 00:17:54 man script

HISTIGNORE=hostname:ls

Linux Commands#Process Management