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Before any astrology can happen, the app must answer a purely astronomical question: where was everything in the sky at that exact instant, seen from that precise spot on Earth? The engine follows a clear, step-by-step pipeline so that every number in your chart traces back to a transparent calculation rather than an opaque black box. The astronomy follows standard treatments such as V. P. Jain’s Elements of Astronomy — the same chain of steps a careful astrologer once worked through by hand using an ephemeris.

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The conversion pipeline

1

Enter local clock time and place

You supply a local clock time and a birthplace. The place fixes a time zone, and the engine uses that to convert your entry to Universal Time (UT) — the global reference clock. For example, 2026-06-01 10:30 in Asia/Kolkata (UTC+05:30) becomes 2026-06-01 05:00 UT. All subsequent calculations run against this single universal instant.
The app handles historical time-zone quirks — war-time offsets, zones that have shifted over the decades — through its built-in place database. When the civil time zone for a historic birth is uncertain, use the Enter coordinates option to set the UTC offset explicitly.
2

Compute tropical longitudes

From the universal instant, the engine calculates each body’s tropical longitude — its position measured eastward from the March-equinox point. The Sun, Moon, Mercury, Venus, Mars, Jupiter, and Saturn each follow well-established orbital models. The lunar nodes Rāhu and Ketu are computed as the points where the Moon’s orbit crosses the ecliptic.
Mean vs. true nodes. Rāhu and Ketu can be expressed as the mean node (a smoothed average motion) or the true node (the instantaneous crossing point). Jyoti Guide uses the mean node by default — the most common convention in jyotiṣa — and places Ketu exactly 180° opposite Rāhu. You can switch this in Chart settings.
3

Subtract the ayanāṁśa

To move from the tropical frame to the sidereal (fixed-star) frame, the engine subtracts the ayanāṁśa — the precessional gap described in Why sidereal? — from every longitude. The result is each body’s position against the actual constellations. Switching the ayanāṁśa setting (Lahiri, Raman, Pushya) changes this single subtraction and therefore shifts the whole chart together. See Ayanāṁśa options for the values each system uses.
4

Derive the Lagna (rising sign)

The houses are anchored to the Lagna — the degree of the zodiac rising over the eastern horizon at birth. Computing it requires the latitude and longitude of the birthplace and the local sidereal time, because the horizon’s angle depends on where on Earth you stand. The Lagna sweeps through all twelve signs roughly once every 24 hours, changing sign approximately every two hours. This is why a precise birth time is essential.
5

Assign whole-sign houses

With the Lagna known, the engine assigns houses. Jyoti Guide uses the whole-sign house system by default: the sign containing the Lagna degree becomes the entire 1st house, the next sign the 2nd house, and so on. Signs and houses align one-to-one, which keeps the chart clean and is the oldest and most widespread house system in classical jyotiṣa.
6

Resolve nakṣatra and pada

Finally, each body’s sidereal longitude is resolved into a nakṣatra (lunar mansion) and pada (quarter). These feed directly into period calculations and divisional charts.

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What the output looks like

At the end of the pipeline every body has a sidereal longitude expressed as a sign, a degree within that sign, a house, and a nakṣatra–pada pair. Everything else in the app — strength scores, daśā periods, transits, compatibility — builds on these primary positions. 
Lagna   1st   Cancer / Karka       17°06′40″   Ashlesha · 1
Sun     11th  Taurus / Vrishabha   16°30′36″   Rohini · 2
Moon     5th  Scorpio / Vrischika  25°43′28″   Jyeshtha · 3   (debilitated)
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Continue reading: now that you know how the positions are built, learn about the twelve signs and nine planets that interpret them — Rāśis & Grahas.