Improved tests and set of default calendar.

app/models/calendar.rb

@@ -212,7 +212,7 @@ returns
     Calendar.all.each {|calendar|
       return if calendar.default
     }
-    first = Calendar.first
+    first = Calendar.order(:created_at, :id).limit(1).first
     first.default = true
     first.save
   end

test/unit/calendar_test.rb

@@ -3,7 +3,7 @@ require 'test_helper'
 
 class CalendarTest < ActiveSupport::TestCase
   test 'default test' do
-
+    Calendar.delete_all
     calendar1 = Calendar.create_or_update(
       name: 'US 1',
       timezone: 'America/Los_Angeles',
@@ -19,7 +19,7 @@ class CalendarTest < ActiveSupport::TestCase
       updated_by_id: 1,
       created_by_id: 1,
     )
-
+    sleep 1
     calendar2 = Calendar.create_or_update(
       name: 'US 2',
       timezone: 'America/Los_Angeles',