I searched all over the internet for this, and the documentation isn\'t really talking about monthly jobs in specific. So I was hoping that someone here could tell me how to do
Whenever doesn't support an :on option as far as I am aware, but you should be able to do
:on
every '0 2 20 * *' do runner "Mailer.send_friend_sheet" end
The '0 2 20 * *' is simply the relevant cron syntax - see http://www.manpagez.com/man/5/crontab/