The Javanese calendar, with the arithmetic shown.
Give it a date — a birthday, today, any date at all — and see its weton, Javanese date, wuku, and mangsa, along with the arithmetic that produced them.
Today
- Javanese date
- Neptu
- Mangsa
Computed in your browser, from the date on this device.
Four cycles running at once, arithmetic you can redo by hand, the kurup handled correctly across history, and a hard line between what is computed and what is inherited.
What is a weton?
A weton is a pair of day names: the day of the seven-day week (Ahad through Setu) and the day of the five-day pasaran week (Legi, Pahing, Pon, Wage, Kliwon). Together they give something like “Jemuwah Kliwon”.
Because five and seven only meet again after 35 days, the same pair recurs every 35 days. That 35-day turn is the selapan — and it is where this site gets its name.
Two further cycles run above those: the wuku, which repeats every 210 days, and the Javanese lunar year that Sultan Agung began in 1633 CE. Four cycles, running at once, each with its own length.
Four cycles, running at once
Every date sits at a position on all four simultaneously. That is why the Javanese reckoning cannot be collapsed into a single table.
| Cycle | Length | Elements |
|---|---|---|
| Pasaran | 5 | Legi, Pahing, Pon, Wage, Kliwon |
| Dina | 7 | Senen, Selasa, Rebo, Kemis, Jemuwah, Setu, Ahad |
| Wuku | 210 | 30 wuku — Sinta, Landep, Wukir … Watugunung |
| Javanese date | 354 / 355 | 12 — Sura, Sapar … Besar |
What you can open here
- ConvertOne date, the full Javanese reckoning — weton, wuku, mangsa, lunar date — with the selapanan dates and the mangsa around it swept from the same instrument.
- CalendarA whole month in the wall-calendar layout — the Gregorian day large, pasaran and Javanese date beneath.
- KurupWhy the Aboge and Asapon reckonings can differ by a day, and how that difference arises.
- SourcesEvery anchor and table the app uses, its source, and an open list of what is still unverified.
How this differs from other weton sites
- Computes pasaran, dina, weton, neptu, and wuku for any date, unbounded in both directions.
- Computes the Javanese lunar date from 1633 CE, with its windu, year, and the kurup that applies — and refuses to compute before that, rather than guessing.
- Puts Aboge and Asapon side by side where they diverge, with the mechanism that separates them.
- Shows the derivation of every figure: anchor, day offset, modulus, result, and the citation behind it.
What is computed, and what is inherited
Computation and interpretation are kept apart, in the code and in the palette. Indigo is for computed values; rubric red is reserved for primbon material and used for nothing else. The interpretive layer is not released: it is waiting on a reviewer familiar with Javanese calendrical practice.
- Computed valueArithmetic. Opens up, and can be redone by hand.
- Traditional materialReserved for primbon and unused so far — that layer has not been released.
- UnverifiedResting on a single source, or outside the range that applies.