Human Design: how Ollin calculates your chart

Human Design combines astrology, the I Ching, the chakra system and genetics into a single map. Put that way, it sounds vague. In reality, the calculation is astronomical arithmetic, and it's either right or wrong.

Where the calculation starts

It takes three things: your date, time and place of birth. From there, Ollin calculates the positions of thirteen celestial bodies at two distinct moments.

Each planetary position falls into one of the 64 sectors of the zodiac that the system calls gates, and within each gate, into one of six lines. Everything else follows from this grid of 26 activations (thirteen for each of the two moments): which Centers are defined, which channels form, what Type you are, how you make decisions.

Your Type, and why it's the first thing we tell you

Your Type comes from the pattern of your defined Centers: Generator, Manifesting Generator, Manifestor, Projector or Reflector. It isn't a personality label. It describes how your energy is available to you.

• If your Sacral Center is defined, you have sustainable energy that comes alive by responding to what shows up, rather than chasing it.
• If you have a motor connected to the Throat without going through the Sacral, your role is to initiate, and informing the people involved spares you half the resistance.
• If you have neither, your strength isn't doing, it's seeing: you thrive when people seek you out, not when you offer yourself.
• If you have no defined Centers at all, you're a mirror of your environment, and where you are matters more than anything else.

Along with your Type comes your Authority: the way your body tells you yes or no before your mind steps in. Some people need to sleep on it, others get an immediate gut response. Knowing which one you are changes far more decisions than you'd expect.

What Ollin calculates that you won't find elsewhere

Beyond the basic chart, the engine produces a range of analyses that usually call for a professional:

• Incarnation Cross: the structure formed by your four main activations
• Variables and Determination: the four arrows, with Color and Tone calculated
• Life cycles and transits: what you're moving through now, and what temporarily completes your chart
• Solar Return: the theme of your year, anchored to your birthday
• Connections and group charts: what emerges between two charts, or within a group of people
• Personal rhythm: a spectral analysis of your cycles, with a projection deliberately limited to 90 days

Birth time, and a bug we had to fix

Being off by an hour can move the Moon six degrees and change gates, lines and, in some cases, your Authority. It's the most sensitive piece of data of all.

That's why Ollin doesn't use a fixed time zone. It calculates the historically correct one for your date, daylight saving time included. It sounds like pedantry, but it was a real bug: Italian summer births were shifted by an hour, and the "strange" charts some people reported were simply wrong. Now there's a dedicated function, with sixteen tests guarding it.

A calculation engine that fails silently is worse than none at all: it produces results that are believable and false.

How we know when we get it wrong

The engine is covered by golden tests: a set of reference charts, calculated and frozen. If a code change alters even a single value, the release is blocked. There are also dedicated tests that check that the gates attributed to a person in the chat context are exactly the ones in their chart, and that the counts per Center add up to the total.

That doesn't guarantee the interpretation will resonate with you. It guarantees the numbers are right.