calenos.com

What It Is

CalenOS positions itself as a “Universal Calendar OS.” More precisely, it is an API platform for multiple traditional calendars, astronomical data, and folk date-selection methodologies, rather than a typical generative AI tool. It first standardizes the calculation of core astronomical data such as moon phases, solar/lunar longitude, Nakshatra, and Tithi, then allows calendar and divination systems such as Thai, Lanna, Chinese, Hijri, and Hebrew to reuse that data.

Core Capabilities

Its technical core is a deterministic algorithm and rules engine: astronomical calculations are based on Jean Meeus algorithms and Suriyayat traditional Thai astronomy. At the methodology layer, rules are described using a JSON DSL rather than code, with an emphasis on auditability and portability. The API currently covers around 60 endpoints, 5 calendar plugins, and nearly 30 methodologies, returning structured results such as Thai riksa, Chinese zodiac, Heavenly Stems and Earthly Branches, Five Elements, Hijri dates, and Hebrew dates. Its value lies in productizing scattered traditional calendar rules into a unified JSON interface.

API, Chinese Support, and Pricing

The documentation lists the Base URL as https://calenos.com/api/. Both V1 and V2 endpoints return JSON and support GET/POST execution, batch execution, One Call, multiple date ranges, timezone parameters, and more. No API Key is currently required, and CORS is open, making it suitable for direct integration into front-end apps or lightweight services. For Chinese support, the site provides a Chinese language entry point and supports methods such as the Chinese lunar calendar, zodiac, Heavenly Stems and Earthly Branches, and Five Elements. However, the interface language parameters explicitly listed are mainly th/en. Pricing has not been disclosed; the site only mentions a free tier with “generous” quotas, while Phase 2 plans include rate limiting and API Keys.

Pros, Cons, and Limitations

The advantages are a low integration barrier, clear response structures, rare cross-tradition coverage, and deterministic calculations that are easy to reproduce and audit. The drawbacks are that it does not offer large-model reasoning or natural language generation capabilities; privacy terms, SLA, commercial pricing, and payment methods are not disclosed; and some traditions such as Vedic, Western, Japanese, and Burmese are still marked as Coming. The methodology list also includes TODO placeholders, so its maturity needs to be tested in practice.

Who It’s For and Access from China

It is suitable for developers building perpetual calendars, date-selection tools, astrology/folk-culture apps, or cross-cultural date display tools, as well as researchers looking to verify traditional calendar rules. Access from China cannot be determined from the available text, and payment methods are not disclosed. If stable commercial use within mainland China is required, it may be worth evaluating local Chinese lunar calendar/perpetual calendar APIs, a self-hosted Swiss Ephemeris service, or alternatives such as Timeanddate.