Using date in cron

A simple way to have a command log output to a file grouping by date is to do something like:

# writes to a file my-command-YYYYMMDD.log
my-command >> my-command-$(date +%Y%m%d).log

But in a cronjob you should escape the % character by prepending it with a backslash like this:

* 0 * * * my-command >> my-command-$(date +\%Y\%m\%d).log

To capture both stdout and stderr:

* 0 * * * my-command >> my-command-$(date +\%Y\%m\%d).log 2>&1