Advanced Ichimoku ② — Time Theory: Base Numbers, Corresponding Numbers, and Change Days

Lesson 2 Overview: The Heart of Ichimoku — Time

Ichimoku Sanjin held that “the market changes not because of price, but because of time.” Time Theory is the most central of Ichimoku’s three theories, and it deals with “when does the turn arrive.”

1. Base Numbers

These are the core time units Ichimoku Sanjin derived from years of market observation.

Simple base numbers: 9, 17, 26
9: one “segment” — short-term change
17: two segments (9 + 9 − 1)
26: one “period” — mid-term change (the same 26 used in the Tenkan-sen, Kijun-sen, and Cloud)

Compound base numbers: 33, 42, 65, 76, 129, 172, 200 … (combinations of the base numbers used to read longer cycles)

2. Change Days (変化日)

A change day is a date with a heightened probability that the market’s direction or character will shift. Major turns — tops and bottoms — often show up around these dates.

How to count (basic method)

Take a meaningful high or low as your starting point (day 1)
Mark the days that land on a base number: day 9, day 17, day 26…
Watch for a turn (reversal) to appear around those dates

Caution: this isn’t “the market will definitely turn on that day” — it’s a “candidate day where a turn becomes more likely.”

3. Corresponding Numbers (対等数値)

This is the idea that the number of days a past wave took tends to repeat, roughly, in future waves.

If the prior rally took 30 days, treat ~30 days as a candidate for the next phase too
Compare day counts between high-to-high, low-to-low, high-to-low, and similar spans
When several corresponding numbers converge on the same date, confidence in that change day rises

4. Using Time Theory in Practice

Set a meaningful turning point (high or low) as your reference
Mark change-day candidates using base numbers (9, 17, 26…)
Mark additional candidates using corresponding numbers
Where candidate dates overlap, treat that date as a “date to watch”
Around that date, weigh it together with wave (Lesson 1) and price (Lesson 3) signals

This Lesson’s Key Takeaways

Ichimoku Sanjin held that “time” is what changes the market — Time Theory is the central pillar.
The base numbers are 9, 17, 26 (and their compounds), and 26 shares a common root with the rest of Ichimoku.
A change day is a “candidate day where a turn becomes more likely” — not a certainty.
Corresponding numbers reflect the idea that the day count of a past wave tends to repeat.
The more base numbers and corresponding numbers overlap on a date, the more confidence you can place in it.

Next lesson: We look at Price-Target Theory, which addresses “how far” a move will go. You’ll learn to calculate target price ranges using four values — V, N, E, and NT.

Verify with official sources

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(Verified: June 2026)