til/rails/set-datetime-to-include-time-zone-in-migrations.md

Set Datetime To Include Time Zone In Migrations

When using Rails and PostgreSQL, your migrations will contain DSL syntax like t.datetime and t.timestamps which will produce columns using the timestamp (without time zone) Postgres data type.

While reading A Simple Explanation of Postgres' Timestamp with Time Zone, I learned that there is a way to configure your app to instead use timestamptz by default. This data type is widely recommended as a good default, so it is nice that we can configure Rails to use it.

First, add these lines to a new initializer (config/initializers/postgres.rb) file.

require "active_record/connection_adapters/postgresql_adapter"
ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.datetime_type = :timestamptz

Alternatively, you can configure this via config/application.rb per the Configuring ActiveRecord docs.

Then, if you have a new migration like the following:

class AddEventsTable < ActiveRecord::Migration[7.2]
  def change
    create_table :events do |t|
      t.string :title
      t.text :description
      t.datetime :start_time
      t.datetime :end_time
      t.timestamps
    end
  end
end

you can expect to have four timestamptz columns, namely start_time, end_time, created_at, and updated_at.

Here is the Rails PR that adds this config option.