How can I add a timestamp to the end of a cron job's output file name?

1  *    * * *   root    php /mix/dostuff.php > "/tmp/dostuff-`date +\%Y-\%m-\%H\ \%k:\%M:\%S`.txt"

Simple as that.

On CentOS 6.6, I use

*/10 * * * * /usr/bin/php -q /var/www/script.php > cron-job-log-$(date +\%Y\%m\%d\%H\%M\%S).txt

it will create a file every 10 min

cron-job-log-20150401124001.txt