Quick cron reference

In the LuCI interface, under System >> Scheduled Tasks, enter (at the top):

# ┌───────────── minute (0–59)
# │ ┌───────────── hour (0–23)
# │ │ ┌───────────── day of month (1–31)
# │ │ │ ┌───────────── month (1–12 or JAN–DEC)
# │ │ │ │ ┌───────────── day of week (0–7 or SUN–SAT, 0 and 7 = Sunday)
# │ │ │ │ │
# * * * * *
#
# ENSURE ALL SCRIPTS HAVE A SHEBANG AT THE TOP, eg: #!/bin/sh
# ENSURE ALL SCRIPTS HAVE BEEN MADE EXECUTABLE, eg: chmod +x /etc/YOUR SCRIPT.sh
#
# PLACE SCRIPTS IN /etc/ SO THEY SURVIVE FIRMWARE UPDATES, eg:
# cat << 'EOF' > /etc/YOUR_SCRIPT.sh
# {SCRIPT GOES HERE}
# EOF
#
# EXAMPLE:
# System configuration backup (SUNDAYS at 0400)
# 0 4 * * 0 /etc/backup_router.sh