Ubuntu - Cron - Schedule a Cron Job at 8 pm on Monday, and Saturday

0 20 * * Mon,Sat /bin/sh script.sh

The above entry in your crontab will make cron execute the script.sh file at 8 pm in every Mondays and Saturdays.

You can make this script run on any other day of the week by providing the day name using a comma-separated list.

However, you should always try to specify numerics value as many cron jobs will not work with the abbreviated values.

The same command specified using the numeric value would be as shown below.

0 20 * * 1,6 /bin/sh script.sh