I'd like to add the date/time to the output of the `history` command in CentOS/RHEL 6. I would like this to apply to all users on the machine by default. This itself is easy. It seems to just be a case of adding:

```
export HISTTIMEFORMAT="%Y%m%d %T  "

```

Where should that be added? I've seen some conflicting info on whether to add this to `/etc/profile` or `/etc/bashrc`. I believe both would work equally well.

Does anyone have any advice as to which file I should use for this specific modification?