Full Stack Application - Where to fill entity fields? | front or back?

First of all i have to indicate that I am new to the area of Full Stack Development and I use JHipster framework to implement my app.

So, let's assume that I have a Post entity with these fields:

Post Entity

name: String,
text: String,
dateCreated: ZoneDateTime,
userID: String

When a user creates a Post, I want to automatically add the dateCreated field as well the userID in the Post entity that will be saved to database. So my question is: Where should I have to fill the model with the userID and dateCreated? In the front-end(Angular) or in the back-end(Spring)? What is the appropriate way?

P.S Sorry for the title selection. I wasn't able to describe it better.