Planetary Hours

Method & Engineering

How Planetary Hours Are Calculated (Step by Step)

This is the procedure a reliable calculator follows. The arithmetic is not the point — the point is getting the boundaries and the sequence correct, in the correct timezone, for the correct civil date.

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Step 1 — Acquire sunrise & sunset (correctly)

  • ✦Use the location’s timezone (including DST rules).
  • ✦Use the local civil date (not UTC date labels).

Step 2 — Compute temporal hour lengths

Let sunrise, sunset, and nextSunrise be local times.

dayLen   = sunset - sunrise
nightLen = nextSunrise - sunset

dayHour   = dayLen / 12
nightHour = nightLen / 12

Step 3 — Build the 24 boundaries

  • Day hour i: [sunrise + (i-1)*dayHour, sunrise + i*dayHour]
  • Night hour j: [sunset + (j-1)*nightHour, sunset + j*nightHour]

Step 4 — Assign planetary rulers

Use the Chaldean order: Saturn → Jupiter → Mars → Sun → Venus → Mercury → Moon (repeat).

  • ✦The first daylight hour starts with the weekday ruler.
  • ✦Continue the sequence continuously through day and night (do not reset at midnight).

Implementation notes

  • ✦Handle polar edge cases (no sunrise/sunset) gracefully.
  • ✦Keep boundaries at second precision to avoid UI drift.
  • ✦12h/24h is display-only; internal math stays in absolute timestamps.

Next: Unequal hours explained · How to read the table

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