What I Learned Coding A Retirement Countdown With AI

Read the full analysis: What I Learned Coding A Retirement Countdown With AI on ThorstenMeyerAI.com

Thorsten Meyer says he built and released Altersteilzeit, a free web app that counts down working days for people in Germany’s partial-retirement block model, in five days with help from the Claude Opus 5.5 coding agent. In an account published October 13, Meyer describes the project’s growth from a one-minute animated film into a site with a daily countdown, a narrated film and games, while stressing that he set the direction and approved the work.

Meyer says he began on Monday, September 28, asking the agent for a short film about the two phases of Altersteilzeit in the block model: a period of regular work followed by an equal period away from work. By Friday, October 2, the project had become a public website. The app asks users for the start date of either phase and their work model, then calculates the corresponding dates and remaining working days.

The app’s features include a daily countdown with milestones and a saying of the day, a film about the user’s phases, and a 3D game collection. Meyer’s article describes a bridge-day finder, calendar exports, a printable calendar, badges and group countdowns, among other features. It says the games connect calendar time to play, with real months, weeks or working days represented in game mechanics. The source account gives differing totals for game modes—describing nineteen games in one passage and fifteen modes in another.

Meyer says all 24 commits were co-authored by the agent. He attributes engineering, testing, translation and production tasks to the AI, including generating voice clips and sound effects. He says he supplied prompts, reviewed the results, selected creative details and approved releases. According to the account, the app has no accounts, cookies or tracking, and performs its date calculations in the browser.

What the Five-Day Build Shows

The account offers a specific example of how a coding agent can contribute to a small software project across development, testing and production, rather than only drafting isolated code. Meyer reports that the agent handled a broad set of tasks, including 3D browser features and translations, while he retained responsibility for the concept, tone and approvals.

For readers considering similar tools, the distinction matters: a fast build does not mean the software appeared without human direction or review. Meyer’s account presents the work as a collaboration, but it is also a first-person project report, not an independent assessment of the app’s reliability, accessibility or development cost. It illustrates what one creator says was possible in this project; it does not establish how quickly other projects can be built.

The app also targets a defined practical need. People in the block model may want to track the working days remaining in a long active phase. A countdown can make that period easier to visualize, while the calendar features connect the calculation to leave planning. The value for users will depend on whether the dates and holiday rules fit their individual circumstances.

From Film to Countdown Site

Altersteilzeit is a form of partial retirement in Germany. In the block model described by Meyer, a person works as usual during an active phase and then has a passive phase of equal length. A four-to-four model, for example, pairs four years of work with four years away from work.

Meyer says his original request was for a one-minute animated film, not a complete retirement-planning product. The daily view, games, language support and other features were added over the next four days. The timeline in his article records changes such as adding a mobile scrolling fix and building the bridge-day finder. He also says the app uses the user’s German federal state and entered leave when calculating working days.

The author describes the site as free and says date information shared through a link is placed after the address’s hash mark, which browsers do not send to a server. These are claims in Meyer’s account; the supplied material does not include an independent technical review or user testing results.

“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 focus

What the Account Does Not Establish

The source is Meyer’s account of his own project. It does not include independent verification of the app’s calculations, security or privacy claims, nor does it report testing by users. It is also unclear from the supplied material how the site handles edge cases in employment arrangements, state holidays or changes to a user’s leave.

Some details need clarification. The article refers to nineteen games in one section and fifteen modes in another, without explaining whether those figures count different things. It also describes support for seven languages and five German dialects, then refers to twelve languages in its account of translations and voice production. The relationship between those counts is not specified.

The report does not give a development budget, a comparison with a conventional build, the agent’s operating costs or user numbers after launch. The speed and scale Meyer describes should be understood as reported project details, not independently measured results or evidence that comparable timelines are typical.

Use, Testing and Future Updates

Meyer’s account does not announce a specific next release or testing milestone. The app is described as publicly available, but the source material gives no user count, feedback summary or schedule for updates. Future reporting could establish whether users find the date calculations accurate across different work arrangements and whether the site’s language and accessibility features meet their needs.

For now, the next steps are practical: users can try the countdown and calendar features, while Meyer may need to correct inconsistencies in the published feature counts and clarify how the app handles unusual work schedules. Any assessment of the privacy claims would require technical details or an independent review beyond the account provided.

Key Questions

What is Altersteilzeit?

Altersteilzeit is a German form of partial retirement. In the block model described by Meyer, a person works through an active phase and then has an equally long passive phase.

What does the app calculate?

According to Meyer, users enter the start date of one phase and select a model, such as four years active followed by four years passive. The app calculates the other date and counts working days, taking the selected German federal state’s public holidays and entered leave into account.

How long did the project take?

Meyer says work began on September 28, 2026, and the public site was ready by October 2. That five-day timeline is his account of the project.

What did the AI agent do, according to Meyer?

Meyer credits the Claude Opus 5.5 coding agent with engineering, testing, language work and production tasks. He says he provided direction, made creative and product decisions, reviewed the output and approved releases.

Have the app’s privacy and calculation claims been independently checked?

Not in the supplied source material. Meyer says calculations happen in the browser and the app has no accounts, cookies or tracking, but his article does not include an independent audit or user-testing results.

Source: ThorstenMeyerAI.com