This question already has an answer here:
This is intentionally a duplicate of the following question (because the answers there are not completely correct, and as a new user I somehow cannot comment there): Editing crontab
ADDED NOTE: The "How do I set up a Cron job?" question too wrongly states that "sudo crontab -e" edits /etc/crontab (it does NOT) - it IS marked as a duplicate of the "Editing crontab" question.
(hoping to get some upvotes here, so I can help correcting wrong answers in the intended way)