Birth Hour and the 12 Earthly Branches Explained

What Are the 12 Two-Hour Blocks?

A day is split into 12 two-hour blocks, each named after one of the 12 earthly branches: Tý, Sửu, Dần, Mão, Thìn, Tị, Ngọ, Mùi, Thân, Dậu, Tuất, Hợi (23:00-00:59, 01:00-02:59, and so on in two-hour steps). This is the actual time unit the whole star-placement calculation runs on, not the hour:minute of a modern clock. One caveat: the Tý block crosses midnight, and under the convention this site locked in after comparing Vietnam's major chart engines, the charting day changes at 23:00: a 23:00-23:59 birth is charted on the next solar day, while 00:00-00:59 stays on that same day.

Why Birth Hour Matters More Than the Date Alone

The Life palace position is found by counting from a fixed starting palace by birth month, then rotating further by birth hour. That means birth hour is what decides which of the 12 palaces the Life palace lands on: two people born on the same date but in a different two-hour block end up with a different Life palace, which rotates every other palace along with it.

If You Do Not Remember the Exact Time

If family only recalls it loosely ("early morning", "around noon"), ask whoever was present at the birth or check a birth certificate before building the chart, rather than guessing a block. A chart built on the wrong hour produces the wrong Life palace, and every reading downstream, including an AI reading, inherits that original error.