Have the following command setup in my crontab to renew the certificate for this blog, and for the main website - thecurlybraces.com

30 3 1 */2 *  /opt/letsencrypt/certbot-auto renew --pre-hook "service nginx stop" --post-hook "service nginx start"  

This causes the command to run,

At 03:30 on day-of-month 1 in every 2nd month.

Output

Upgrading certbot-auto 0.12.0 to 0.14.1...  
Replacing certbot-auto...  
Creating virtual environment...  
Installing Python packages...  
Installation succeeded.  
Saving debug log to /var/log/letsencrypt/letsencrypt.log

-------------------------------------------------------------------------------
Processing /etc/letsencrypt/renewal/thecurlybraces.com.conf  
-------------------------------------------------------------------------------
Cert is due for renewal, auto-renewing...  
Running pre-hook command: service nginx stop  
Renewing an existing certificate  
Performing the following challenges:  
http-01 challenge for thecurlybraces.com  
http-01 challenge for blog.thecurlybraces.com  
Waiting for verification...  
Cleaning up challenges

-------------------------------------------------------------------------------
new certificate deployed without reload, fullchain is  
/etc/letsencrypt/live/thecurlybraces.com/fullchain.pem
-------------------------------------------------------------------------------

Congratulations, all renewals succeeded. The following certs have been renewed:  
  /etc/letsencrypt/live/thecurlybraces.com/fullchain.pem (success)
Running post-hook command: service nginx start  

Just putting this here for reference, and with the hope that it might be useful for someone else.