Changing date format in frontpage content

Hello, my site is running Drupal 8.2 and I cannot figure out how to change the date format on my promoted to frontpage content.

What I am getting at the moment is:

Submitted by webadmin on Thu, 09/29/2016 – 11:39

And what I want to show is just


I have tried changing the default date format and it’s not working. I guess Drupal is using the fallback date format, but it is impossible to change.

I would like to know where in the code I have to look for the ‘Submitted by…’ part and the date format.

Drupal version: