Most of a reading is description. The period sequence is the part with dates on it, and it is the part almost no other framework has at all. It is also simple enough to follow yourself, which means any date you are given can be checked rather than believed.

Where the sequence starts

It starts from the Moon. Divide the zodiac into twenty-seven segments of 13°20′ each — the nakshatras — and find the one the Moon occupied at your birth. Each is assigned one of nine planetary lords in a fixed, repeating order:

Ketu, Venus, Sun, Moon, Mars, Rahu, Jupiter, Saturn, Mercury.

That lord rules your first period. And because the Moon was somewhere inside the segment rather than at its start, part of that first period was already spent before you arrived — the fraction of the nakshatra the Moon had crossed is the fraction of the period already gone. This is the detail that makes birth time matter here, and it is also why two people born on the same day can be years apart in the sequence.

How the years are allotted

Each lord gets a fixed number of years, and they total 120:

Ketu 7 · Venus 20 · Sun 6 · Moon 10 · Mars 7 · Rahu 18 · Jupiter 16 · Saturn 19 · Mercury 17

After your starting lord finishes, the next in the order takes over for its own allotment, and so on. That is the whole of the top level. If you know your starting lord and how much of it was left at birth, you can lay out the major periods of an entire life on a single sheet of paper.

Why 120. It is the classical full span of a life in this system, not a prediction about yours. Nobody is promised the whole cycle, and reaching the end of it is not a thing the sequence claims.

The levels nest by the same proportions

Here is the part that trips people up, and it is genuinely elegant once seen. Every period divides into sub-periods using the same nine proportions, starting from its own lord.

So a Venus major period of 20 years begins with a Venus sub-period. Its length is Venus's share of the whole: 20/120 of 20 years, which is 3 years and 4 months. The next sub-period is the Sun's — 6/120 of 20 years, or 1 year. Then the Moon's, 10/120 of 20 years, and around the order it goes.

Then each sub-period divides again by the same rule. Your file prints three levels with start and end dates, and the rules it used are written inside it, so you can reproduce any figure it gives you.

The mistake that shifts every date

This one is worth knowing because it is common and it is invisible. The proportions are of solar motion, not of calendar days. A period is a fraction of 360° of the Sun's travel, and the year those degrees take is not exactly 365.25 days.

Split a period proportionally in days and your boundaries drift — enough to land a sub-period change on the wrong side of a date you care about. If two sources give you dates a day or two apart, this is usually the reason, and the one doing it in degrees is the one to trust.

How deep is worth going

The system keeps subdividing — below the third level there are named levels going down to fractions of a day. It is arithmetically fine and practically meaningless, because the precision of the arithmetic exceeds the precision of your birth time. A level that changes every few hours is being computed from a time you know to the nearest fifteen minutes.

Three levels is where your file stops, deliberately. If your birth time is uncertain at all, even the third is worth treating as approximate — the free check tells you how much your own chart tolerates.

What the dates do and do not tell you

A period lord does not deliver events. What it does is say which part of your chart is being emphasised for a stretch of years, and which of its promises are most available. A strong, well-placed lord in a supportive period is a window; a difficult one is a stretch where the same effort returns less. Neither is a verdict, and what to do inside a hard one is a separate and more useful question.

Once you can read the sequence, the other thing it unlocks is comparison. Two people's sequences run at the same time and interact, which is why a marriage needs both charts rather than one.

Your own sequence, three levels deep with dates and the reasoning printed alongside, is in the Complete file.