How to create Cron jobs in Ubuntu

Check if cron is enabled:
sudo systemctl is-enabled httpd

If not found, install like so:
sudo apt update
sudo apt install cron

Enable it, if not enabled:
sudo systemctl enable cron

Edit logged-in users crontab
crontab -e

For example enter the below to run a job at 1:40 AM UTC (ET+4h) every Tuesday and Thursday.
40 5 * * TUE,THU /usr/local/myjob.sh

Save the file and quit.
Reload cron like so:
sudo service cron reload

Make sure the script files have all execute permissions like so :
chmod a+x myjob.sh (the owner of the file can be different from who is running it with crontab -e

If crontab keeps opening in nano or other editors and you are old-school like me and prefer vi, then do this:
export VISUAL=vi

Where does Cron Log?
grep cron /var/log/syslog