A Retirement Countdown Project In 16 Versions: Lessons From AI

🔍 Read the full analysis: A Retirement Countdown Project In 16 Versions: Lessons From AI on ThorstenMeyerAI.com

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Developer Thorsten Meyer says an AI coding agent helped him build and publish Altersteilzeit, a free web app for people counting down working days around German partial retirement, in five days. What began on September 28, 2026, as a request for a one-minute animated film had become, by October 2, a public site with a daily countdown, a film, games, language options and planning tools, according to Meyer’s account.

Meyer describes the project as a collaboration with Claude Opus 5.5, which he says co-authored all 24 commits. He provided directions, made product decisions and approved releases; the agent handled much of the coding, testing, content production and deployment. The account is Meyer’s report of his own project, not an independent assessment of the agent’s performance.

Users enter a date for the start of either the active or passive phase of an Altersteilzeit block model, then select a model from 1:1 to 5:5. The app calculates the other date and counts weekdays, accounting for public holidays in the selected German federal state and leave entered by the user. Its tools include a morning countdown, milestones, a printable calendar, calendar export and a bridge-day finder.

The site also includes a short narrated film and a set of 3D games that connect gameplay to calendar time. Meyer’s version history describes the project expanding day by day: languages and a daily view on the second day, more games and planning features on the third, narration and sound effects on the fourth, and final approval plus German dialect options on the fifth. The source article refers to both 19 games and 15 game modes at different points, so the exact distinction between games and modes is not fully explained.

Human Decisions Behind the Build

The account offers a concrete example of how an AI coding agent can contribute to a small software project when a person supplies the concept and stays responsible for decisions. Meyer says the agent took on a broad set of production tasks, from browser-based 3D features and test scripts to translations, voice clips and deployment. Those details show the scope of the work he reports, but they do not establish that the same speed or output would be typical for other projects.

For readers, the app’s value is practical rather than technical: it brings workday calculations, milestones and retirement-themed entertainment into one tool. Its stated privacy design also matters for users entering personal dates. Meyer says the app has no accounts, cookies or tracking, and performs calculations in the browser. He says shared dates are stored in the URL fragment, which is not sent to a server in standard browser requests. These are descriptions from the developer; the source does not provide an independent privacy audit.

The project also illustrates where Meyer says human judgment remained necessary: setting the tone, choosing voices and dialects, deciding what the narrator reads, and approving public releases. The distinction is relevant to readers evaluating AI-assisted work: an agent can execute many assigned tasks, but the account still places responsibility for the product’s direction and sign-off with its human creator.

How the Five-Day Project Grew

Altersteilzeit is a German partial-retirement arrangement. In the block model described by Meyer, a person works as usual during an active phase and then has a passive phase away from work; a 4:4 arrangement, for example, pairs four years in each phase. The app is designed to count remaining working days rather than simply calendar days.

Meyer says his initial request on Monday, September 28, was for a short animated film about those two phases. He then added date calculations and game prototypes before publishing the site that evening. Over the next four days, the project added language support, a daily view, more games, badges, planning tools, narration and sound. The development timeline and feature counts come from the project creator’s October 13 account.

The source describes substantial production output: about 18,000 lines of JavaScript and Python, 15 test scripts, more than 1,800 text strings per language in 12 languages, and 1,224 voice clips. Meyer says parallel sub-agents worked on larger tasks such as dialect translation. The source does not provide the code, test results or an external review that would let readers independently verify those figures or evaluate quality.

“The interesting part is not how much an AI agent can build, but what was still left for me to do.”

— Thorsten Meyer, describing the project’s central question

What the Account Does Not Verify

The reported timeline, code volume, language coverage, test scripts and media totals come from Meyer, who built the app. The article does not include independent testing, a review of the source code or confirmation from the AI provider. It also does not report user numbers, accessibility testing, ongoing maintenance plans or whether the app’s holiday and working-day calculations have been checked against official guidance.

There is a count that needs clarification: Meyer calls the feature a set of 19 games, while another passage says the game is playable in 15 modes. The account does not explain whether those figures refer to separate games, modes, or different versions. The source also describes seven languages at one point and later says twelve languages, alongside five German dialects; it does not lay out exactly how those language counts relate to one another.

The privacy statements likewise remain the developer’s claims. Meyer explains how dates in shared links are placed after the “#” in a URL and says calculations happen in the browser, but no third-party security or privacy assessment is provided. The article does not say whether those design choices have been independently reviewed.

Public Use and Further Verification

Altersteilzeit was already publicly available by October 2, according to Meyer, and the October 13 article presents the completed project and its development process. The source does not announce a future release date, a planned feature, or an independent evaluation. It is not clear whether Meyer intends to maintain or expand the app, or how updates will be handled.

The next useful evidence for readers would be independent checks of the date calculations, language and accessibility features, and privacy behavior, along with clarification of the games and language counts. Until then, the project is best understood as a developer’s detailed account of one AI-assisted build, rather than a verified benchmark for how quickly AI agents can produce reliable public software.

Key Questions

What is Altersteilzeit?

Altersteilzeit is a German partial-retirement arrangement. In the block model described by Meyer, a person works during an active phase and then spends a matching period in a passive phase.

What does the app calculate?

Users enter a phase start date and choose a model from 1:1 to 5:5. The app calculates the other date and counts working days, using weekdays, public holidays for a selected German federal state and leave entered by the user, according to Meyer.

How did AI contribute to the project?

Meyer says Claude Opus 5.5 worked as a coding agent on engineering, testing, translations, voice clips and deployment. He says he set the direction, made product decisions and approved releases.

Is the app’s privacy design independently verified?

No independent audit is described in the source. Meyer says there are no accounts, cookies or tracking and that calculations happen in the browser, but those details are reported by the developer.

How many games does the app have?

Meyer describes 19 games in one passage and says the game is playable in 15 modes elsewhere. The article does not explain how those counts differ.

Source: ThorstenMeyerAI.com