Use Date instead of Datetime. Nobody cares about the exact hour.

db/migrate/20160801163421_add_expires_at_to_member.rb

@@ -24,6 +24,6 @@ class AddExpiresAtToMember < ActiveRecord::Migration
   # disable_ddl_transaction!
 
   def change
-    add_column :members, :expires_at, :datetime
+    add_column :members, :expires_at, :date
   end
 end

db/schema.rb

@@ -581,7 +581,7 @@ ActiveRecord::Schema.define(version: 20160801163421) do
     t.string   "invite_token"
     t.datetime "invite_accepted_at"
     t.datetime "requested_at"
-    t.datetime "expires_at"
+    t.date     "expires_at"
   end
 
   add_index "members", ["access_level"], name: "index_members_on_access_level", using: :btree