I use Let's Encrypt on Ubuntu 17.10 server with Apache HTTP server. In crontab I have:
15 3 * * * /usr/bin/certbot renew
If I check expire date with:
sudo certbot certificate
I get report for my two certificates with expire date 2018-03-18. So far, so good.
But - I got an email from email@example.com with notification that certificate for the same domain(s) will expire on 2018-01-16.