Enable time tag in History command in Linux

The Bash history feature is an invaluable details/ information which allows users to recall commands previously entered into their shell with relative ease. This makes it easy to enter repeated commands and keep track of what was done on a system.

By default, however, a user is unable to see when these commands were actually entered. When auditing a system, it can sometimes be useful to see this type of information, for example when trying to determine how and when a file may have gone missing on the file system. Since Bash version 3, however, you are able to enable time-stamping of entries for review later.

Applicable versions of Bash provide the environment variable HISTTIMEFORMAT which you can set for this purpose. Although it is empty by default, you can simple assign a time format string to enable time-stamping.

First run this command :

user@localhost :~$ history
   53  vi /etc/fstab
   54  umount /ebs
   55  mount /ebs/local

Enable timestamp in history command

To enable time stamp on your bash history type following command on your terminal:
    user@localhost :~$ export HISTTIMEFORMAT="%F %T "

Again execute history command : 
   user@localhost:~$ history
   53  2016–03–02 08:27:38 vi /etc/fstab
   54  2016–03–02 08:27:38 umount /ebs
   55  2016–03–02 08:27:38 mount /ebs/local

More help for set time format in date command manual page :
   man date

Now you can Add it to your .bashrc end of the file so it’s always there.
   user@localhost:~$ vi .bashrc

# ~/.bashrc: executed by bash(1) for non-login shells.
    export HISTTIMEFORMAT="%F %T "