Can create files w/ Time/date stamps from the shell (touch file_`date +%Y%m%d`) but this does not work when the same command is entered in the crontab.

Typically, when commands/scripts don't work work from the shell and not from cron, it is because the cron environment isn't the same. Generally, it's because cron's PATH is different from your user's PATH.

Also, keep in mind that cron uses the bourne shell as it's default. That's why you are better off placing your touch command in a script like this:

#!/bin/ksh

export PATH=.. # whatever your PATH and shell is

touch file_`date +%Y%m%d`
# end script