Timezone and Database config

Hello, I am trying to use Brazil Timezone but I don’t know how to config it as default on my phoenix project.
I tried to use Tzdata but I am not sure if it is what I need.
I am new to this area and I would like to know if there is any solution to set the entire application to UTC-3 which is the standard in Brazil or if I must configure it each time a value is inserted and retrieved in the database.