MySQL and UTC

I’m about to install write.freely on my server but have one question before I start. In the official install guide, it mentions that if I use MySQL then the database timezone needs to be UTC. Is this essential? What happens if it’s not? I assume that it’s also ok to use Mariadb? I already have a few databases on my server and they are set to my local timezone ie europe/london. My system, and PHP is also set to this aswell so I don’t really want to have to change it all for the sake of a single web app. If it is essential to change to UTC then I guess I could just use SQLite instead.