Getting the Chart Right

How Much Birth Time Matters

Each part of a chart runs on its own clock. Know which parts your birth time can support.

Every layer has a clock

The lagna is the fast hand

Foundations said the lagna changes sign roughly every two hours. Finer: all 360° rise in a day, so the lagna moves about 1° every 4 minutes on average.

Average is doing some work there. Signs don't rise at an even pace, and the spread widens with latitude. From a minute-by-minute sweep with this app's engine:

| Latitude | Quickest sign rises in | Slowest sign rises in |
|---|---|---|
| 13°N (Chennai, Bengaluru) | ~99 min | ~132 min |
| 28°N (Delhi) | ~85 min | ~139 min |
| 52°N (London) | ~50 min | ~172 min |

Aquarius, Pisces and Aries are the quick risers. At 13°N the lagna's pace ranges from about 0.9° to 1.2° per four minutes.

Each layer runs on its own clock

Rough averages for how often each piece of a chart changes:

| Piece | Changes about every |
|---|---|
| D60 lagna (0°30′) | 2 minutes |
| D10 lagna (3°) | 12 minutes |
| D9 lagna (3°20′) | 13 minutes |
| Lagna sign | 2 hours |
| Moon's pada | 6 hours |
| Moon's sign | 2¼ days |
| Sun's sign | a month |
| Saturn's sign | 2½ years |

The Vargas chapter warned that a D60 from a rounded time is fiction. This table shows why: a clock that changes every two minutes can't be read from a time known to the half hour.

The dasha clock runs on the Moon

Vimshottari dates come from how far the Moon has travelled through its nakshatra. The Moon moves about 13° a day, roughly 0.55° an hour.

So one hour of birth-time error moves the Moon about 4% of a nakshatra, and moves every dasha date by about 4% of the birth dasha lord's years: roughly three months if that lord is the Sun, and roughly ten months if it's Venus.

The lagna isn't the only thing a birth time touches. Timing does too.

Is this birth time good enough?

Recorded: "about 6:30, give or take 15 minutes." The chart cast for 6:30 has the lagna at 14° Leo.

Lagna sign. At about 1° per 4 minutes, ±15 minutes is about ±4°, so the lagna lies between 10° and 18° Leo. The whole range is Leo, so the sign is safe and so are all the whole-sign houses.

D9 lagna. Leo's navamsas are 3°20′ wide. 10°–13°20′ is Cancer navamsa, 13°20′–16°40′ is Leo, and 16°40′–20° is Virgo. The range touches three D9 lagnas, so the D9's houses are not safe.

Moon. In 15 minutes it moves only about 0.14°. Unless it sits right on a boundary, its sign, nakshatra and pada are safe.

Verdict: read the D1 with confidence. Treat the D9 lagna as open. Leave the D60 alone.

What survives an unknown time

With only a date:

Planet signs are mostly secure, since everything but the Moon moves slowly.
The Moon's sign changes during about 4 days in 9, so check whether it does on that date.
The Moon's nakshatra almost always changes within a day, so dasha dates can't be fixed.
There is no lagna, which means no houses, no house lords and no divisional lagnas.

That still leaves real work. Sign placements, dignities, conjunctions, and Moon-based techniques like gochara all hold if the Moon's sign is secure. What you mustn't do is quietly assume a time, often noon, and then read houses from it as if they were known.

Where birth times go wrong

Recorded times fail in ordinary ways:

Rounding. A suspicious number of people are born at exactly :00 or :30.
Memory. "Just before sunrise" and "around lunchtime" are windows, not times.
Which moment. Traditions differ on exactly which moment of birth counts, so even a careful clock reading carries a little uncertainty.
Time zones. The zone and any daylight-saving rule in force at that place on that date matter, and historical rules differ from today's.

None of this is anyone's fault. It's why the next level exists.

Remember it

Two hours a sign, four minutes a degree, thirteen minutes a navamsa, two minutes a D60. And an hour of Moon is months of dasha.

Terms introduced here

Birth-time sensitivity: The lagna moves about 1° every 4 minutes; the D9 lagna changes every 13 minutes or so; an hour of Moon motion moves dasha dates by months.