The ‘history’ commands does not display the exact date and time of the commands executed. It just shows a numeric id followed by  the command executed by the current user. Here is one way of putting a time stamp –

 export HISTTIMEFORMAT='%F %T  '

To make sure that it works every time you login or restart your machine, put it in $HOME/.bash_profile

Other useful environment variable related to the history command are –

1. HISTFILE
The name of the file in which command history is saved.

2. HISTFILESIZE
The maximum number of lines contained in the history file.

3. HISTIGNORE
A colon-separated list of patterns used to decide which command lines should be saved on the history list.

4. HISTSIZE
The number of commands to remember in the command history.