OpenAI co-founder Greg Brockman posted on X that GPT-4 finished training four years ago today. The model was released publicly in March 2023. Replies noted its early sense of capability and the pace of later progress. Commenters compared it to Stable Diffusion 1.4 trained around the same time and joked that GPT-5 training finished five years ago. Several asked Brockman to mark the date by releasing the parameter count or open-sourcing the model.