Why I've got no crontab entry on OS X when using vim?

Question

I would like to use cron on my Mac. I choose it over launchd, because I want to be able to use my new knowledge on Linux as well. However, I cannot seem to get

Answer 1

In user crontab (crontab -e) do not put the user field.

Correct cron is:

0-59 * * * * echo "Hello World"

Syntax with user field is for /etc/crontab only:

0-59 * * * * mollerhoj3 echo "Hello World"