Planetary ingress dates in tropical and sidereal frames
Why the same planet crosses tropical and Lahiri-sidereal sign boundaries on different dates and why neither timestamp may replace the other.
Frame comparison · released 2026-08-18
Shared fact substrate
The planet follows one calculated trajectory. An ingress is a solved crossing of that trajectory against a boundary defined by the selected zodiac frame.
Required shared inputs
- Planetary longitude function
- Search interval
- Ephemeris and time scale
- Frame-specific boundary
- Root-finding tolerance
Tropical view
The root occurs when tropical longitude crosses a multiple of 30 degrees measured from the equinox-defined origin, with direction and solver tolerance retained.
Lahiri-sidereal view
The root occurs when the Lahiri-transformed longitude crosses its corresponding 30-degree boundary, generally at a different instant.
Where they agree
Direction of motion and the ordered physical trajectory are shared. Both calculations should reproduce from the same ephemeris and declared tolerance.
Where they disagree
The dates and sign names differ because the boundaries differ. The time gap is not a calculation error and should not be compressed into one approximate “ingress season.”
Preservation policy
Persist each crossing with frame, boundary, direction, UTC instant, solver bracket, tolerance, and calculation version.
Prohibited synthesis
Do not average ingress dates, use the tropical date with a sidereal sign name, or select the crossing nearest a known milestone after the fact.
What empirical comparison requires
Treat tropical and sidereal outputs as separate candidate models. Any performance claim requires preregistered features, outcomes, horizons, baselines, model-selection policy, multiplicity control, and prospective scoring that retains misses and abstentions.
Method sources
These sources define calculation and namespace policy. They do not determine which astrology system is true.
- Celestial timing reference library
Maha Celestial
Frame-explicit ingress, station, lunation, repeated-crossing, and Vimśottarī chronology conventions.
Boundary: A deterministic event date is not evidence that the event predicts a real-world outcome.
- Lahiri ayanāṁśa calculations
Maha Celestial
Maha’s declared transformation from retained tropical longitude to a separate Lahiri-sidereal longitude.
Boundary: Selecting Lahiri defines one sidereal convention; it does not establish that sidereal astrology is superior or empirically valid.