Cron, not working

Question

Issue

I have this cronjob.

5 12 * * * find /var/www/html -name "*.php" -o -name "*.htm*" -o -name "*.css" | tar -cf /var/www/export/$(date +"%m-%d-%Y")-backup-fs.tar.gz -T -

But it is not working, even no errors came to configured email.

When I run this command manually, it works.

I tried set up the rights to 777.

Where is the catch?

Thanks.