0,30 00-16 * * * command
There is nothing wrong with this crontab entry. It should run the command on the hour and half hour from midnight thru 4:30pm every day.


Did you mean to have it NOT run at 4:30? You'd need two lines:

0,30 00-15 * * * command # Runs from midnight to 3:30pm
0 16 * * * command # Runs at 4:00pm