Edit .bashrc and replace the PS1 variable with:
NOW=$(date +%Y-%m-%d) PS1="\[\e[36m\][$NOW\[\e[m\]\[\e[36m\]@\[\e[m\]\[\e[36m\]\t]\[\e[m\] \[\e[32m\]\u\[\e[m\]@\[\e[32m\]\h\[\e[m\]:\[\e[31m\]\w\[\e[m\]\\$ "
This will result with
<html>[YYYY-MM-DD@HH:MM:SS] user@root:/path$ _</html>
Since .bashrc is executed last, this change cannot be made for all users