Namkha Calculator

Python library for calculating Namkha thread-cross color schemes in the tradition of Chögyal Namkhai Norbu Rinpoche, with all the methods covered in the source text.¹ Classical Tibetan astrology calculations were added for cases where the source refers to them for complete instructions.²

Table of contents

• Development status
• Usage
  • Key types
    • User input
    • Timezone handling
    • Input validation and errors
    • Result
  • Calculation notes
    • Latitude "trimming"
• Contributing
• Licence
• Acknowledgments
• References

Development status

TODO

• Year Namkha calculation (CNNR and Classic)
• Birth-time edge-case warnings
• [WIP] Automatic historical timezone detection from coordinates
• Month Namkha calculation
• Day Namkha calculation
• Hour Namkha calculation
• More pre-calculated test cases
• Further investigation into the high-latitude regions problem

Usage

from datetime import datetime

import namkha_calculator as nc

subject = nc.Subject(
    name="John Doe",
    gender=nc.Gender.MALE,
    birth_datetime=datetime(1985, 3, 15, 14, 30),  # naive local time
    birth_location=nc.Location(latitude=52.52, longitude=13.40, name="Berlin"),
)

result = nc.calculate_namkha(
    namkha_type=nc.NamkhaType.YEAR,
    subject=subject,
    method=nc.CalculationMethod.CLASSIC,  # or CalculationMethod.CNNR
)

for aspect in result.harmonized_aspects:
    threads = ", ".join(e.value for e in aspect.harmonization_seq)
    conflict = " (conflicted)" if aspect.is_conflicted else ""
    print(f"{aspect.name.name}: center={aspect.center.value}, threads=[{threads}]{conflict}")

for note in result.calculation_notes:
    print(f"[{note.note_type.name}] {note.message}")

Key types

User input

Subject – birth data for one person (or another entity with a known birth/creation time, e.g. a company).

All fields are keyword-only.

birth_timezone is normally omitted – the library derives the timezone from the birth coordinates and date. To set it explicitly, use nc.zone("Europe/Berlin") for a named IANA zone, or nc.fixed_offset(timedelta(hours=..., minutes=...)) when the birth time is known only as a bare UTC offset.

Timezone handling

Timezone data is bundled with the package: an IANA tzdb zoneinfo tree compiled with the backzone file, so results are identical on every operating system, and zones that tzdb merged away for post-1970 equivalence keep their own real pre-1970 histories (an Amsterdam birth in summer 1935 gets the true Dutch +1:19:32, not the +1:00 of the Brussels zone; wartime Stockholm keeps Sweden's DST-free clocks, not Berlin's ect.). The birth timezone is resolved as follows:

• Explicit timezone given – used as-is. nc.zone(key) (a zoneinfo.ZoneInfo from the bundled data) and datetime.timezone fixed offsets are accepted; anything else (including pytz zones) is rejected with TypeError.
• Omitted, birth from 1970 on – the IANA zone covering the coordinates. This is a certain derivation: tzdb guarantees zone histories from 1970, so even zones that changed later for political reasons resolve to the correct historical rules.
• Omitted, birth before 1970 – tzdb only guarantees each zone's history that far back for its reference city, and modern zone borders must not be projected into the past. The birthplace is looked up in bundled historical world maps (1880–1960, from historical-basemaps): if the covering zone's reference city belonged to the same country as the birthplace in the birth year, that zone applies; otherwise the zone of the nearest reference city within the birth-year country applies. The TIMEZONE_ESTIMATED caution is attached, or TIMEZONE_BORDERS_UNCERTAIN when the maps around the birth year disagree (see Calculation notes). This case is still work in progress.
• Omitted, open water or outside every timezone – on open water, the nautical Etc/GMT±N zone for the longitude; where the coordinates match no timezone at all, the longitude's mean solar time. Both get the TIMEZONE_ESTIMATED caution and the LOCAL_MEAN_TIME notice. Whichever zone applies – derived or explicitly given – a birth before standard time in that zone (the tzdb "LMT" era, roughly pre-1880s–1912 depending on country) uses the mean solar time of the birth longitude itself, which is more accurate than any zone's reference-city approximation. The LOCAL_MEAN_TIME notice is attached.

Birth dates are proleptic Gregorian; a Julian-calendar source date must be converted first (see the PRE_GREGORIAN_DATE caution under Calculation notes).

Input validation and errors

Subject validates its input at construction and raises instead of computing from inconsistent data:

• birth_datetime must be naive – TypeError otherwise (the timezone belongs in birth_timezone).
• birth_timezone must be None, a zoneinfo.ZoneInfo, or a datetime.timezone; anything else is rejected with TypeError.
• A fixed offset must lie within the range real timezones have used, UTC−16 to UTC+16, or ValueError – an offset outside it is a data-entry error. The range is that wide because zones that counted dates across the Date Line carry solar offsets shifted by a whole day (pre-1845 Manila ran -15:56). Named zones are not checked: their offsets come from real tzdb data.
• An explicit timezone must be consistent with the location's longitude, or ValueError: the (standard-time) clock may run at most 2.5 h behind or 3.5 h ahead of the longitude's mean solar time. Every historical timezone fits these bounds; the behind bound is tighter because a clock behind the sun pulls dawn towards clock midnight. This check is skipped at latitudes of 60° and above, where we consider the day start is a fixed local hour and solar time is irrelevant (see Latitude "trimming").

calculate_namkha raises ValueError – never degrades silently – when:

• the birth instant never existed in its timezone (a time skipped by a spring-forward clock change, or a whole date removed by a dateline change, e.g. 2011-12-30 in Samoa);
• the birth year falls outside the supported range, 1551–2598 (limited by the bundled ephemeris);
• an extreme behind-the-sun fixed offset at 56–60° latitude lands on the rare date (~1 per year) whose dawn drifts across clock midnight onto a neighboring date – no real timezone can trigger this.

Location – latitude, longitude, optional name.

NamkhaType – YEAR, MONTH, DAY, HOUR.

CalculationMethod – CNNR (Chögyal Namkhai Norbu Rinpoche's tradition) or CLASSIC ("classical" Tibetan astrology tradition). Only YEAR accepts CNNR; all other types use CLASSIC.

Result

NamkhaCalculationResult

HarmonizedAspect

Calculation notes

PERIOD_BOUNDARY (caution) is attached when the birth time falls within 5 minutes of a calculation-period boundary (for YEAR, the Tibetan year start/end). That close to a boundary the result can flip to the neighboring period, so the birth time must be precise.

HIGH_LATITUDE (notice) is attached when abs(latitude) >= 60.0. Above this limit the library falls back to a fixed 5:00 AM day-start instead of civil twilight, which affects birth period boundary detection.

AMBIGUOUS_LOCAL_TIME (caution) is attached when the naive birth time falls in a fall-back clock change and so occurs twice; the standard-time reading is used unless on_summer_time says which reading is correct (then AMBIGUOUS_LOCAL_TIME_RESOLVED, a notice, is attached instead). A birth instant that never existed in the timezone – a time skipped by a spring-forward clock change, or a whole date removed by a dateline jump – is rejected with a ValueError rather than noted.

TIMEZONE_ESTIMATED (caution) is attached when no timezone was given and it could not be derived from the location and date with certainty (pre-1970 birth, or birth on open water); the best historically recorded regional time was used.

TIMEZONE_BORDERS_UNCERTAIN (caution) replaces TIMEZONE_ESTIMATED – the two are mutually exclusive – when the historical map snapshots on either side of a pre-1970 birth year disagree about which country held the birthplace, so even the country whose time applied is uncertain. Short-lived changes between two maps (e.g. the 1939–1941 Soviet occupation of eastern Poland, which decreed Moscow time) are invisible to the maps and cannot be resolved automatically by any open dataset we know of. Right now the remedy is research: establish the birthplace's legal time from historical sources (the World Historical Gazetteer is a good starting point for a place's administrative history) and pass it as birth_timezone.

LOCAL_MEAN_TIME (notice) is attached when the birth clock time was read from the longitude rather than from civil timezone rules: a birth before standard time in its region, on open water, or outside every timezone.

PRE_GREGORIAN_DATE (caution) is attached to births before the Gregorian calendar was adopted at the birth place (15 October 1582 at the earliest, as late as the 1920s in some regions), as a reminder that a Julian-calendar source date must be converted to Gregorian.

Latitude "trimming"

In the Tibetan calendar a new day begins at dawn, not at midnight. The library defines dawn as the start of civil twilight – the moment the sky first starts to brighten before sunrise (in traditional texts, when one can see the lines on the palm of their hand). This boundary decides which Tibetan hour (and therefore Tibetan day, month, etc.) a given birth time belongs to.

Closer to the poles (i.e. at higher latitudes) this breaks down. For long parts of the year there is no dawn: the midnight sun in summer, when the sky never fully darkens, and the polar night in winter, when it never properly brightens. On those dates civil twilight does not start (or does not end), so there is no dawn to anchor the day to and the astronomical lookup returns nothing.

As far as we know, Tibetan astrologers have not agreed on a solution to this problem. For now the library does the following: it "trims" the usable latitude range at 60° north/south. Below that limit it uses the real civil-twilight dawn. At or above it, it falls back to a fixed 5:00 AM local time (a convention also found in Tibetan tradition) as the day-start and attaches the HIGH_LATITUDE notice. This issue is a subject of further research.

Contributing

Issues, PRs and questions are welcome.

See CONTRIBUTING.md for details.

Licence

GPL-3.0-or-later. The package bundles:

• historical world border maps from aourednik/historical-basemaps (GPL-3.0) – bundling them is why this project is GPL rather than MIT;
• an IANA tzdb zoneinfo tree compiled with backzone data (public domain);
• a filtered JPL DE440 ephemeris (public domain).

Timezone boundary lookups use timezonefinder (MIT), whose boundary data derives from timezone-boundary-builder (ODbL).

Acknowledgments

Whatever wisdom this contains belongs to the Tibetan astrological traditions and their holders; whatever faults it contains are our own.

We thank everyone who supported the Namkha Calculator project financially – your help means a great deal to us, and it sustained us through a lot of obstacles.

We would also like to express our gratitude to: Migmar Tsering, Maria Rita Leti, Adriano Clemente, Alexander Khosmo and Tatiana Ulyanova for their guidance on Tibetan astrology; and to the Gakyil of Merigar East – Oana Marcu and Krisztina Balla for their invaluable help in providing indispensable educational materials.

References