The Chinese version of TikTok “Douyin” is introducing a “teenage mode” that will limit the number of times children under the age of 14 spend on the short-form video app to 40 minutes a day. The measure will apply to all Douyin users under the age of 14 who have registered for the app using their real names, Beijing-based ByteDance recently announced in a statement . Douyin will also be unavailable to those users between 10 p.m. and 6 a.m., the owner of TikTok and Douyin added. The company also urged parents to help their children register with real names,…