KP Transit Timing: How to Verify Every Crossing Instant

KP practitioners do not ask what a chart means. They ask when. A sub lord change is the event, and the answer is a clock time somebody acts on: a query is judged in the sub lord running at that second, a favourable window opens and closes inside an hour. That makes KP transit timing the least forgiving thing an astrology API publishes. A natal longitude that drifts by an arcsecond is invisible; a crossing instant that drifts by ten minutes moves a reading into the neighbouring sub lord, and nothing in the response tells you it happened. This article walks the arithmetic connecting position accuracy to clock accuracy, the three ways a window scan silently loses events, and a reproducible procedure for checking a crossing instant against an external authority.

Why is a KP crossing time really a position claim?

A crossing instant is not measured in seconds. It is derived from a longitude, so the error that can be bounded is a position error, and the clock error is that divided by how fast the body moves. One arcsecond is therefore worth a fraction of a second on the Moon and many minutes on a retrograde outer planet, which makes any timing claim that does not name the body meaningless.

Read the last column as the real specification. A Moon sub lord change published to the minute is a modest claim: the Moon has to be wrong by half an arcminute before the minute changes. A Saturn ingress to the minute is two orders of magnitude harder, and it arrives in the same response shape. Accuracy belongs in arcseconds; the clock is what geometry does to it afterwards.

Ready to build on this? The Vedic Astrology API returns a full KP boundary scan for any window in one request. See pricing.

How wide is a KP sub lord window, and how long does a planet stay inside one?

The 249 KP divisions are not equal. Each nakshatra of 13 degrees 20 minutes is split in the Vimshottari proportions, so a sub spans anywhere from 40 arcminutes to 2 degrees 13 arcminutes depending on which lord owns it. The narrowest is the sub of the Sun. The Moon crosses it in a little over an hour, which is the practical resolution a KP timing feature has to respect. Dwell times below are at the 13.998 degrees per day NASA JPL Horizons gives for the Moon on the morning of 2026-09-28.

The dwell column is arithmetic, and a real response confirms it. On 2026-09-28 the Moon entered the sub of the Sun at 09:46 UTC and left at 10:54 UTC. To the second the stay is 68 minutes 35 seconds, against 68.6 minutes predicted from the lunar rate that morning. Across September 2026 the same endpoint reports 268 sub lord crossings for the Moon from one request. At that density a five minute error consumes seven percent of the narrowest window. For what those lords signify, the KP sub lord guide covers the system; this article is about whether the timestamp beside it is true.

How do you check a crossing instant against NASA JPL Horizons?

Three steps, no key needed for the external half, and it works against any provider that publishes both a crossing time and the sidereal offset it used. Ask the vendor when the crossing happened, ask NASA where the body was then, subtract the offset, and see how far the result sits from the claimed boundary. Checking a position at a given time is the sibling procedure, covered in how to verify astrology accuracy against NASA JPL; this is the inverse, the time at a given position.

1. Take the published minute. POST /vedic-astrology/kp/rasi-changes for the Sun in April 2026 returns one event, the sidereal Aries ingress, at 2026-04-14T01:41:00, the crossing instant rounded to the nearest minute.
2. Read the sidereal offset. GET /vedic-astrology/kp/ayanamsa?date=2026-04-14&time=01:41:00 returns 24.12936884 degrees, the KP Newcomb value. It moves about 0.14 arcseconds a day, so it is constant across the minute you are testing.
3. Ask NASA JPL Horizons where the Sun was across that minute. The Horizons API returns apparent geocentric ecliptic longitude keylessly. Subtract the offset from both readings: a correct claim brackets the boundary.

curl -s --get "https://ssd.jpl.nasa.gov/api/horizons.api" \
  --data-urlencode "format=text" \
  --data-urlencode "COMMAND='10'" \
  --data-urlencode "CENTER='500@399'" \
  --data-urlencode "EPHEM_TYPE='OBSERVER'" \
  --data-urlencode "START_TIME='2026-04-14 01:40'" \
  --data-urlencode "STOP_TIME='2026-04-14 01:42'" \
  --data-urlencode "STEP_SIZE='1m'" \
  --data-urlencode "QUANTITIES='31'"

# 2026-Apr-14 01:40      24.1287821
# 2026-Apr-14 01:41      24.1294628

Subtract the offset from each reading. At 01:40 NASA puts the Sun 2.11 arcseconds short of the boundary; at 01:41 it is 0.34 arcseconds past. The ingress falls inside that minute, nine seconds before the 01:41 the API publishes, checked with one keyless query and two numbers RoxyAPI publishes. The same test at second precision, on four crossings across three bodies and four decades:

The last two rows are the argument of this article. Saturn sits 0.05 arcseconds from the boundary, a sixth of the Moon residual, and on a body creeping backwards at 0.048 degrees per day that is still 22 seconds of clock. The same position accuracy is under a second on the Moon. A timing claim only means something once it names the body. Roxy Ephemeris reads the NASA JPL DE440 ephemeris directly and is verified against NASA JPL Horizons, with tolerances on the methodology page and a reproducible dataset in the open astrology API benchmark.

Which three ways does a transit scan silently lose events?

A boundary scan walks a body forward in steps and asks, at each step, whether a boundary was passed. Three things go wrong in that loop, and none of them raises an error or empties a field. The scan returns a list with something missing, and the caller cannot tell. RoxyAPI pins every one with tests against an external authority, which is what the verification above is for.

The step that wraps 0 degrees

Longitude is circular and arithmetic is not. In the step where a body passes 0 degrees the two samples read something like 357.3 and then 4.3, so a guard that rejects any step whose endpoints are far apart throws away the one step that mattered. The tell is easy to run: ask for the sidereal Aries ingress and see whether you get it.

curl -s -X POST https://roxyapi.com/api/v2/vedic-astrology/kp/rasi-changes \
  -H "X-API-Key: $ROXY_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"planet":"Sun","startDate":"2026-04-01","endDate":"2026-04-30"}'

{"planet":"Sun","startDate":"2026-04-01","endDate":"2026-04-30","totalChanges":1,
 "changes":[{"date":"2026-04-14","time":"01:41","datetime":"2026-04-14T01:41:00",
 "fromSign":"Pisces","fromSignLord":"Jupiter","toSign":"Aries","toSignLord":"Mars"}]}

An empty array there is the signature of the wrap defect, and a full solar year is the second test: twelve ingresses, with Aries between Pisces and Taurus. The Moon shows it once every sidereal month. On 2026-09-28 it crosses 0 degrees at 04:37 UTC and POST /vedic-astrology/kp/sublord-changes returns nine sub lord crossings for that day, including the wrap as KP number 249 into 1, Saturn sub into Ketu sub, with the nakshatra lord moving from Mercury to Ketu in the same row.

The tail of the window

The second loss is at the other end. A walk that stops as soon as the next step would pass the end date drops everything inside that final partial step, up to half a day for the Moon and a day or more for a slow body. It is invisible in one request and obvious in two: ask for a single day, then for two days containing it, and count the events inside the shared date. Disagreeing counts mean the tail is being dropped.

A retrograde crossing labelled backwards

The third is not a loss but an inversion, and it corrupts the reading rather than the count. If the from and to labels come from the boundary degree rather than the direction of travel, every retrograde crossing is published with its two ends swapped, and a KP scan inherits the fault twice over because the sub lord and the nakshatra lord both move with it. The test is a body that crosses one boundary in both directions inside a few months:

{"planet":"Saturn","totalChanges":2,"changes":[
 {"datetime":"2044-06-25T00:58:00","fromSign":"Scorpio","toSign":"Libra"},
 {"datetime":"2044-08-28T04:25:00","fromSign":"Libra","toSign":"Scorpio"}]}

Saturn leaves Scorpio backwards in June and re-enters it forwards in August. Jupiter does the same at the Pisces boundary in 2010, out on 3 November and back in on 4 December. If a provider labels both crossings of one boundary identically, the labels are read off the degree and direction is not in the answer at all.

How do you scan a KP window in your own timezone?

Two calls. Resolve the city to an IANA timezone, then hand that timezone to the scan, because both dates are read as calendar days in the timezone you send rather than as UTC days. That is what makes a request for one Indian day return one Indian day. Sending Asia/Kolkata for 2026-09-28 returns the nine Moon crossings of that Indian calendar day in local clock time, and the sidereal Aries ingress that reads 01:41 UTC reads 07:11 in Chennai.

# Step 1: resolve the city to its IANA timezone
curl -s "https://roxyapi.com/api/v2/location/search?q=Chennai" \
  -H "X-API-Key: $ROXY_API_KEY"
# {"cities":[{"city":"Chennai","country":"India","latitude":13.0878,
#   "longitude":80.2785,"timezone":"Asia/Kolkata","utcOffset":5.5, ...}]}

# Step 2: scan the KP sub lord boundaries for that local day
curl -s -X POST https://roxyapi.com/api/v2/vedic-astrology/kp/sublord-changes \
  -H "X-API-Key: $ROXY_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"planet":"Moon","startDate":"2026-09-28","endDate":"2026-09-28","timezone":"Asia/Kolkata"}'

import { createRoxy } from '@roxyapi/sdk';

const roxy = createRoxy(process.env.ROXY_API_KEY!);

const { data: places } = await roxy.location.searchCities({ query: { q: 'Chennai' } });
const { timezone } = places.cities[0];

const { data } = await roxy.vedicAstrology.getKpSublordChanges({
  body: { planet: 'Moon', startDate: '2026-09-28', endDate: '2026-09-28', timezone },
});

for (const change of data.changes) {
  console.log(change.datetime, change.fromKp, change.toKp, change.toSublord);
}

import os
from roxy_sdk import create_roxy

roxy = create_roxy(os.environ["ROXY_API_KEY"])

places = roxy.location.search_cities(q="Chennai")
timezone = places["cities"][0]["timezone"]

changes = roxy.vedic_astrology.get_kp_sublord_changes(
    planet="Moon",
    start_date="2026-09-28",
    end_date="2026-09-28",
    timezone=timezone,
)
for change in changes["changes"]:
    print(change["datetime"], change["fromKp"], change["toKp"], change["toSublord"])

Both scans take the same body: planet (one of the seven grahas, Sun through Saturn), startDate, endDate, timezone, plus ayanamsa and nodeType. A window may span up to 365 days, and a range ending before it starts is rejected with a 400 naming the problem rather than an empty list. The response carries totalChanges and a chronological changes array: sub lord rows carry fromKp, toKp, fromSublord, toSublord and the two nakshatra lords, rasi rows carry fromSign, fromSignLord, toSign and toSignLord. Each instant is found to the second and its time is that instant rounded to the nearest minute. Full schemas are on POST /vedic-astrology/kp/sublord-changes and POST /vedic-astrology/kp/rasi-changes, both runnable in the browser with no signup and no key.

What should you ask any KP transit endpoint before you build on it?

Five checks, in the order that finds problems fastest. Each is a single request with an unambiguous right answer, so a shortlist of transit providers can be filtered in ten minutes without reading a line of marketing. Run them against every candidate, including this one.

1. Does it report the 0 degree crossing? Ask for the sidereal Aries ingress for the Sun in the relevant April. An empty array means the wrap is being dropped, and so is one Moon ingress every sidereal month.
2. Does a one day window agree with a wider one? Count the events inside a shared date from a one day and a three day request. A shortfall is a dropped tail.
3. Does it know which way the planet was moving? Find a boundary a slow body crosses twice in one retrograde loop. Both crossings labelled identically means direction is not in the answer.
4. Does it publish the sidereal offset it used? Without the ayanamsa value at the instant no external check is possible, and this is also where two providers most often differ for reasons that are a school choice rather than a bug.
5. Does it say which timezone the dates are read in? A window read as UTC days when you meant local days shifts the whole answer by hours, silently.

FAQ

What is a KP sub lord change and why does the exact time matter?

In Krishnamurti Paddhati the zodiac is divided into 249 unequal sub lord segments, and the sub lord running at a given moment decides whether an event signified by the star lord manifests. Practitioners time queries, muhurtas and horary judgements on those boundaries, so the crossing instant is the answer rather than a detail. The narrowest sub spans 40 arcminutes, crossed by the Moon in about 69 minutes.

How accurate are the KP transit timings from the RoxyAPI Vedic Astrology API?

Crossing instants are refined to the second and published rounded to the nearest minute. Checked against NASA JPL Horizons at four crossings across three bodies and four decades, they put the body between 0.03 and 0.30 arcseconds from the claimed boundary. Because a clock error is a position error divided by the speed of the body, that envelope is under a second on the Sun and Moon and about 22 seconds on a retrograde outer planet.

Can I get KP sub lord change times in my local timezone?

Yes. Send timezone as an IANA name such as Asia/Kolkata, a fixed offset such as +05:30, or decimal hours, and both the requested dates and the returned times are read in that zone, so one date really is one local day. Resolve the name from a city with GET /location/search, which returns the IANA timezone beside the coordinates. The default is UTC.

Does a KP changes endpoint report the sidereal Aries ingress?

It should, and it is the fastest test of whether a transit scan handles the wrap at 0 degrees. A request for the Sun across April 2026 on POST /vedic-astrology/kp/rasi-changes returns the ingress at 2026-04-14 01:41 UTC, 07:11 in India. A provider returning an empty array for that month is dropping every crossing inside the step that spans 0 degrees, not only this one.

How do I verify an astrology API transit time myself?

Take the published crossing instant and the sidereal offset the API used at that instant, then query NASA JPL Horizons for the apparent ecliptic longitude of the same body at the same moment. Subtract the offset and compare with the boundary the API claimed. Horizons needs no key, so the check is two requests and one subtraction, and it works on any vendor that publishes its ayanamsa.

Conclusion

Transit timing is where an insight API becomes a claim about the world, and the only defence is arithmetic anyone can repeat. Every scan and instant above is live on the Vedic Astrology API, part of 258+ endpoints across 18+ insight domains on one key, backed by 12,000+ automated tests of which 3,000+ are locked to named external references. Run the five checks against us first.