Ah, interesting…thats pretty frustrating. That should say config :ash_graphql, ...

Here is the relevant error message if its not set

   No type configured for utc_datetimes!

    The existing default of using `:naive_datetime` for `:utc_datetime` and `:utc_datetime_usec` is being deprecated.

    To prevent accidental API breakages, we are requiring that you configure your selected type for these, via

        # This was the previous default, so use this if you want to ensure no unintended
        # change in your API, although switching to `:datetime` eventually is suggested.
        config :ash, :utc_datetime_type, :naive_datetime

        or

        config :ash, :utc_datetime_type, :datetime

    When the 1.0 version of ash_graphql is released, the default will be changed to `:datetime`, and this error message will
    no longer be shown (but any configuration set will be retained indefinitely).