The newsletter
Cycle readings of the markets that matter, the reasoning behind them, and the occasional deep dive into method. For readers who want the argument, not the headline.
Read on SubstackMarket Zeitgeist
Every market has a zeitgeist. Cycles tell you which one you are in.
A zeitgeist is the mood of a time. In markets, in the economy and in the world around them, that mood has a length, a phase and a direction, and it can be measured. Market Zeitgeist measures it: research for readers, ready-made scanners for observers, and an API for teams that build their own analysis.
One method, several fields
Cycles do not stop at the stock exchange.
The same detection and forecasting routines are applied wherever rhythmic behaviour shows up in data. Financial markets are the core; the other fields inform the readings.
Markets & assets
Equities, indices, FX, commodities, crypto
Dominant cycles, phase and projections per symbol and timeframe.
Economy
Growth, inflation, rates, liquidity
Longer cycles in macro series and how they align with market cycles.
Geopolitics & society
Conflict, sentiment, generational patterns
Recurring patterns in the environment markets operate in.
Natural cycles
Solar activity, geomagnetism, climate
Physical rhythms with a documented relationship to human behaviour.
Who it is for
From a first look to a full integration.
Observers
See the current cycle position without building anything
Ready-made scanner pages for markets and assets, updated on a schedule, plus the research newsletter for the reasoning behind the readings.
Analysts & fund teams
Run your own scans, keep your own process
The analyzer web app for any symbol and timeframe, and API access when the results should land in your own tools.
Quants & builders
Cycle methods inside your systems
Tested backend routines behind a REST API and an MCP server; the Cycles AI skill lets AI coding tools build screens and pipelines on top of it in hours, not weeks.
Research & tools
Five ways in.
The Pro application
Prepared scanner pages for markets and assets, and the analyzer web app for your own symbols and timeframes. A subscription, booked online once the new account system is live; today under cycle.tools.
Open the analyzerThe Cycles API
Dominant cycle detection, cyclic RSI, phase and consensus scores, cycle forecasts, as REST endpoints and an MCP server. Access can be activated on a usage basis: you get a key, pay for what you use, no membership required. Larger plans and the AI tooling come with Cycles IQ.
Request API accessCycles for AI
The MCP server for AI clients, the Cycles AI skill that teaches a model how to run an analysis, and interpretation skills that turn a cycle chart into a clean written reading. Available to Cycles IQ members.
How it worksCycles IQ
The full stack for serious practitioners, with a person behind it.
- Full Cycles API access, the MCP server for Claude, ChatGPT and Cursor, and all AI skills
- The advanced cycle analyzer application with extended tools and screens
- Pre-built applications and dashboards to jump-start your own screens
- All-access pass to Lars's tools, including feature updates, maintenance and support
- A 2-hour individual onboarding session, ongoing 30-minute sessions
- One-time fee plus annual maintenance, individual offer, NDA required
AI
Cycle analysis that language models can run, and read.
The engine is reachable from AI tools, and the rules for using and interpreting it ship as skills. The model does not guess what a cycle chart means; it follows the same interpretation rules an analyst would. The AI tooling is part of the Cycles IQ program. Why the skills matter, in one page.
MCP server
The Cycles engine inside your AI client
Claude, Cursor and other MCP clients call cycle detection, CRSI and forecasts directly. Sign-in through your Market Zeitgeist account, no keys pasted into prompts.
Cycles AI skill
How to run an analysis, and which endpoint does what
A packaged skill that explains the method to the model: the order of steps, which endpoint serves which purpose, and what a valid result looks like. AI coding tools build screens and pipelines on the API from it.
Chart interpretation skills
Hand a cycle chart to the model, get a clean reading
Prepared skills read the cycle charts you created and return a structured, plain-language interpretation. The interpretation rules are predefined in the skill, which keeps hallucination and misreading out of the result.
Method
Measured, not assumed.
Every reading starts from the data: detect the dominant cycles in a series, score their stability, locate the current phase, and only then project. The same routines run in the newsletter, in the scanners, in the analyzer and behind every API call. Cycle lengths are not fixed in advance; they are found in the data and re-measured as it changes.
- Decoding the Hidden Market Rhythm, Part 1: Dynamic Cycles — the method for finding and trading dominant cycles, with indicator source code (2nd edition, 2017)
- Decoding the Hidden Market Rhythm, Part 2: Metonic Cycles — a non-linear approach to cycles that influence financial markets (2014)
- Finalist at the Technical Analyst Awards 2022 in two categories, Best Specialist Product/Research and Most Innovative New Product, for the cycle analysis technology behind the FSC cycles app
- Lars von Thienen serves on the board of the Foundation for the Study of Cycles
Every market moves in cycles, and the cycles morph: a length that dominated a series for two years fades, another takes over, and the right side of the chart no longer matches the one you calibrated on. For twenty-five years I have built the detrending, spectral and validation routines that measure this in the here and now instead of assuming it. What changed is the application layer: with the method encoded as skills, you describe the screen and the AI builds it. The measurement took decades. Using it takes an afternoon. Lars von Thienen, founder of Market Zeitgeist and developer of the WhenToTrade cycle engine, author of Decoding the Hidden Market Rhythm, board member of the Foundation for the Study of Cycles
Start with the research. Talk to us about the rest.
The newsletter is open to everyone. API access and Cycles IQ begin with a short conversation about what you want to do.