What It Takes To Build A Retirement Countdown Alongside An AI Coding Agent

🔍 Read the full analysis: What It Takes To Build A Retirement Countdown Alongside An AI Coding Agent on ThorstenMeyerAI.com

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Developer Thorsten Meyer says he built Altersteilzeit, a free web app for people tracking a German partial-retirement schedule, with the coding agent Claude Opus 5.5 over five days, from September 28 to October 2, 2026. Meyer describes a project that grew from a one-minute animated film into a public website with a working-day countdown, a narrated film, games and multiple language options; he says he directed the work and approved releases.

Meyer’s account, published October 13 on ThorstenMeyerAI.com, describes an app for Altersteilzeit in the block model. Under the arrangement described, a person works as usual during an active phase and then takes an equally long passive phase. The app asks users for the start date of one phase and a model, ranging from 1:1 to 5:5, then calculates the other date.

The countdown is based on working days from Monday to Friday, with public holidays for the user’s German federal state and entered leave deducted, Meyer writes. The resulting dates feed a daily display with milestones and a progress ring, calendar exports, a printable calendar and a tool for finding bridge days. The project also includes a short narrated film and a collection of games that use time in the retirement schedule as their structure.

Meyer says the app was developed through 24 commits co-authored by Claude Opus 5.5. The agent produced code, ran tests, recorded work and supported deployment, according to his account. Meyer says he supplied direction, made decisions about the app’s tone and features, reviewed the outputs and approved releases. His description reports the project’s scope and process; it does not provide an independent audit of the code or a comparison with other development methods.

A Countdown Built Around Personal Dates

The project offers a concrete example of how a coding agent can be used in a small software build: not just to generate a feature, but to support work across engineering, testing, localization and media. Meyer says the agent helped produce thousands of lines of code, test scripts, translations and audio clips. Those figures come from the developer’s account and have not been independently verified here.

For users, the app’s stated purpose is to make a long employment schedule easier to follow day by day. Its combination of personalized dates, milestones and games turns the same calendar data into several interfaces. Meyer also says privacy was a design rule: no accounts, cookies or tracking, with calculations performed in the browser. If users share a link containing dates, he says those dates are stored after the “#” in the web address, rather than being sent to the server in the request.

The account also shows where human review remained part of the work. Meyer says he chose the humor, visual concept, voices and dialects, and made decisions about legal-page contact details. The example therefore documents a particular division of labor, rather than showing that a coding agent can independently decide what a product should be or whether it is ready to release.

From Film Prompt to Public App

Meyer says the project began on Monday, September 28, with a request for a short animated film counting the working days in an Altersteilzeit schedule. The initial idea expanded as he and the agent worked through features. By the first evening, he writes, the site was online with legal pages; later work added the daily countdown, games, translations, audio and other tools. He says he approved the release on Friday, October 2.

The app’s game design ties play to the user’s calendar. In Meyer’s examples, game levels represent years or months, while working days, public holidays and leave affect gameplay. He says the project included 19 game options, although another passage in his account refers to fifteen game modes. The material does not explain whether those counts refer to different versions or categories.

Meyer also describes a substantial localization and production effort: the site was presented in seven languages and five German dialects, and he reports 1,224 voice clips, 17 sound effects, 15 test scripts and roughly 18,000 lines of JavaScript and Python. These are figures supplied by the author of the project account, not measurements verified by an outside source.

“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 lesson

Counts and Independent Checks

The account comes from Meyer, the developer, and does not include an independent technical review, external user feedback or performance data. It is not clear how much time the project would have required without the agent, or how the claimed development pace compares with a conventional workflow. Meyer’s stated counts also differ: one passage describes 19 games, while another says the active phase is playable in 15 modes. The account does not reconcile those figures.

Other details are not established in the supplied material, including how the app handles changes to holiday calendars, whether its calculations have been checked against official rules for every German federal state, and how many people have used it. The privacy and functionality descriptions are Meyer’s statements; no separate verification is provided.

Use and Verification Ahead

Meyer’s account identifies no planned product update, independent review or user milestone. The immediate next step for readers who want to evaluate the claims is to examine the public app and its legal and privacy information directly, rather than treating the project description as an audit. Any future reporting would benefit from checking the date calculations, privacy behavior, accessibility and availability of the stated language and game options.

For the development story, the open question is how the tool performs beyond its creator’s build process: whether people find the countdown useful, whether its calculations match their individual arrangements and how much correction or maintenance the code requires. No user data or follow-up evaluation is included in Meyer’s account.

Key Questions

What is Altersteilzeit?

Altersteilzeit is a German form of partial retirement. In the block model described by Meyer, a person completes an active work phase and then a passive phase of equal length.

What does the app calculate?

Users enter the start date of either phase and select a model from 1:1 to 5:5. Meyer says the app calculates the other date and remaining working days, accounting for weekdays, state public holidays and leave entered by the user.

What did the AI coding agent do?

Meyer says Claude Opus 5.5 helped write and test code, manage localization and produce audio and other project assets. He says he set the direction, made product decisions and approved releases.

Is the app’s performance independently verified?

No independent verification is included in the supplied account. The development figures, feature descriptions and privacy statements are attributed to Meyer, who built the app.

Source: ThorstenMeyerAI.com