True Solar Time — The Hour's True Position

Clock time is not always your BaZi hour. Longitude correction and Daylight Saving must be accounted for.

Clock Time Is Not True Solar Time

The time on your clock follows your time zone — every place in a zone reports the same time. But the sun's position varies across that zone. True Solar Time (TST) is anchored to the sun itself — noon is when the sun reaches its highest point at YOUR location.

BaZi uses True Solar Time, not clock time.

Why Longitude Matters

Australian Eastern Standard Time (AEST) is anchored to longitude 150°E — but Sydney sits at 151.2°E, Melbourne at 144.96°E:

• Sydney: (151.2 − 150) × 4 minutes = +4.8 minutes. Clock noon ≈ TST 12:05.
• Melbourne: (144.96 − 150) × 4 = −20.2 minutes. Clock noon ≈ TST 11:40.

So Sydney and Melbourne born differ in hour-conversion. A Melbourne person born at clock 11:00 has TST ~10:40 — still in the previous hour-branch.

Daylight Saving Time Also Must Be Stripped

NSW, VIC, TAS, SA observe DST (AEDT, UTC+11) from October to April. Births during DST need clock time reduced by 1 hour first, then longitude correction:

Example: 25 December 1986, 3:00am Sydney —

• Strip DST: 2:00am
• Add longitude correction: 2:04:48
• TST ≈ 2:04 — Ox hour (1–3am)

Without the correction: 3:04 falsely places the person in Tiger hour (3–5am) — completely different chart.

China-Born Users Too

Mainland China runs on a single time zone (UTC+8) anchored to 120°E — but the geography is vast:

• Beijing (116.4°E): clock noon ≈ TST 11:46 (14 min slow)
• Shanghai (121.5°E): clock noon ≈ TST 12:06 (6 min fast)
• Urumqi (87.6°E): clock noon ≈ TST 09:50 (130 min slow!)

For Western-China births, the correction is large enough to shift the hour-branch entirely.

How Minglitang Handles This

Minglitang's chart tool automatically computes longitude correction and DST adjustment based on your birth city and time — you enter clock time and city, the system converts to True Solar Time internally.

Next step

If you don't know your exact birth time, see "Can't find your exact birth time?" for guidance.