Update README about generating invoices

README.md

@@ -188,9 +188,12 @@ Cron tasks
 
 You may want to run cron jobs for repetitive tasks.
 
-To generate invoices on the first day of each month, here at 3 am:
+The command that generates invoices should be run every day, so that invoices
+for new subscriptions are created automatically.  On the first day of
+each month, invoices will be generated for all subscriptions.
+This will run the command at 23:59 every day:
 
-`0 3 1 * * /home/coin/venv/bin/python manage.py charge_subscriptions`
+`59 23 * * * /home/coin/venv/bin/python manage.py charge_subscriptions`
 
 To send reminder emails for membership fee expiration: