Yes, the training is based on predicting a missing word. At first, such a task allowed GPT2 to generate paragraphs that were surprisingly coherent, at the user'

Yes, the training is based on predicting a missing word. At first, such a task allowed GPT2 to generate paragraphs that were surprisingly coherent, at the user's request. ChatGPT added a novel ability of conversation. Regarding timestamps, the training did include many examples of timestamps in JSON format.