Ecto.Migration.timestamps

You're seeing just the function timestamps, go back to Ecto.Migration module for more information.

timestamps(opts \\ [])

Adds :inserted_at and :updated_at timestamp columns.

Those columns are of :naive_datetime type and by default cannot be null. A list of opts can be given to customize the generated fields.

:inserted_at - the name of the column for storing insertion times. Setting it to false disables the column.
:updated_at - the name of the column for storing last-updated-at times. Setting it to false disables the column.
:type - the type of the :inserted_at and :updated_at columns. Defaults to :naive_datetime.