This monkey patch of rails_admin allows me to set the timezone for rails_admin models explicitly, while the rest of the app runs on utc.

gistfile1.rb

require 'rails_admin/config/fields/base'

module RailsAdmin
  module Config
    module Fields
      module Types
        class Datetime < RailsAdmin::Config::Fields::Base

          def value
            value_in_default_time_zone = bindings[:object].send(name)
            return nil if value_in_default_time_zone.nil?
            pacific_time_zone = ActiveSupport::TimeZone.new('Pacific Time (US & Canada)')
            value_in_default_time_zone.in_time_zone(pacific_time_zone)
          end
        end
      end
    end
  end
end