The count here is days from one public announcement to the next named model in the same line. It is not days until the old model was switched off. Side models are left out: the o-series, Codex, the mini and nano variants, and GPT-5.3.
The early gaps were long. GPT-1 was published on 11 Jun 2018. GPT-2 followed on 14 Feb 2019, 248 days later. GPT-3 was introduced on 28 May 2020, 469 days after GPT-2. ChatGPT, then running on GPT-3.5, launched on 30 Nov 2022, 916 days after GPT-3. GPT-4 arrived on 14 Mar 2023, 104 days after that.
GPT-4 Turbo was announced on 6 Nov 2023, 237 days after GPT-4. GPT-4o followed on 13 May 2024, 189 days later. GPT-4.5, a research preview, was introduced on 27 Feb 2025, 290 days after GPT-4o. GPT-4.1 reached the API on 14 Apr 2025, 46 days after that preview. ChatGPT got GPT-4.1 on 14 May, a month later. GPT-5 was released on 7 Aug 2025, 115 days after the API date for GPT-4.1.
From GPT-5 the gaps are 97 days to GPT-5.1 on 12 Nov 2025, 29 days to GPT-5.2 on 11 Dec 2025, 84 days to GPT-5.4 on 5 Mar 2026, 49 days to GPT-5.5 on 23 Apr 2026, 77 days to GPT-5.6 general availability on 9 Jul 2026, and 56 days to GPT-6 Astra on 3 Sep 2026. The Register counts the same 77 days from GPT-5.5 in April to GPT-5.6 on 9 Jul, then Astra on 3 Sep.
Astra to GPT-6 Sol is 19 days. Sol shipped on 22 Sep, with Luna. GPT-6.1 Sol shipped on 29 Sep, 7 days later. As of 1 Oct it has no successor in this count. Two announcement dates are one day earlier than Microsoft's API version stamp. That stamp lists GPT-5.1 as 13 Nov 2025 and GPT-5.5 as 24 Apr 2026. Each stamp sits between two gaps, so four numbers move by a day: the 97 becomes 98, the 29 becomes 28, the 49 becomes 50, and the 77 becomes 76. The 19 and the 7 do not move.
Retirement is a different clock. GPT-4o was removed from ChatGPT on 13 Feb 2026 and stayed in the API. A short gap to the next name is not a short time until the old endpoint dies.
On 12 Sep 2026, Anthropic's Dario Amodei wrote: "We must slow the pace at which we improve the capabilities of AI models." The Register notes he was repeating a staff statement, "Pacing the Frontier." Ten days later Anthropic shipped Opus 5.5 and OpenAI shipped GPT-6 Sol and Luna. OpenAI then canceled the October release of GPT-6.1 Astra and paused training on its newest models. On 29 Sep it shipped the smaller GPT-6.1 Sol anyway, into ChatGPT Work, Codex, and the API. Ordinary ChatGPT chat did not get it that day.
Editorial
I counted announcement to announcement because that is the clock a person wiring a model actually feels. The pause that landed was on GPT-6.1 Astra, the model that did not ship, and on a training run. The name in Work, Codex, and the API still changed seven days after Sol.
OpenAI said improvements in caching and inference let it serve Sol and Luna at lower cost, and that it cut their API prices by 50 percent compared with GPT-5.6 promotional pricing. The Register says OpenAI did that by leaving high-performance workloads to Astra. A 19-day gap does not, by itself, prove that capability jumped. It does prove that the label you just learned is no longer the current one. Amodei asked to slow capability improvement. The shipping record held one unreleased frontier model and kept the model list moving.
The early table is not a straight fall. GPT-3's 916 days is the long life in this count, and GPT-4o still had 290 days before GPT-4.5. After July the gaps are 56 days, then 19, then 7. That stretch sits next to the September ask to slow down.