title: Phoenix framework Ecto give default value to timestamp
body: <p>I would like to know how auto fill "updated_at" and "inserted_at" columns generated by timestamp().</p>
  
  <p>The goal is to not specify these values because it has to be automatic.
  I know how to do with other columns.</p>
  
  <pre><code>schema "users" do
    field :newsletter, :boolean, default: false
  
    timestamps(type: :utc_datetime)
  end
  </code></pre>
  
  <p>I have tried</p>
  
  <pre><code>schema "users" do
    field :newsletter, :boolean, default: false
    field :inserted_at,:utc_datetime, default: :utc_datetime
    field :updated_at,:utc_datetime, default: :utc_datetime
  end
  </code></pre>
  
  <p>But it seems it doesn't work or changes are not taken in account when I run:</p>
  
  <pre><code>mix ecto.migrate
  </code></pre>
  
  <p>Is my code wrong or do I use the wrong command line?</p>
  
  <p>In my SQL schema I have</p>
  
  <pre><code>newsletter  BOOLEAN DEFAULT FALSE NOT NULL,
  inserted_at TIMESTAMP             NOT NULL,
  updated_at  TIMESTAMP             NOT NULL,
  </code></pre>
  
  <p>And doesn't matter what I try, I can't have "DEFAULT TIMESTAMP" on the two last lines.</p>
  
  <p>Must I drop the table before it can work?</p>