Casting Qi Men Charts in the US & Canada: How to Enter a Western Longitude

Why Western Longitudes Are Negative

Charting tools follow the international convention: east is positive, west is negative. Beijing at 116.4°E is entered as 116.4; New York at 74°W must be entered as -74.

Getting the sign wrong is not a small error: entering New York as +74° (which is 74°E, near Pakistan) shifts the True Solar Time by about ten hours — the double-hour and even the day pillar all derail, and the resulting chart has nothing to do with you.

How to Find Your Longitude

Three ways, fastest first:

The tool’s GPS button: in the Qimena charting form, tap “Auto GPS” — after the browser permission prompt, the signed longitude is filled in automatically. This is the most error-proof way;
City presets: New York, Los Angeles, London, Sydney and other overseas cities are built into the dropdown;
Google Maps: long-press your location on the map; the second number in the popup coordinates is your longitude (shown as negative in the Americas — copy it as-is).

North American Longitude Quick Reference

City	Longitude	City	Longitude
New York	−74.01	Vancouver	−123.12
Los Angeles	−118.24	Toronto	−79.38
San Francisco	−122.42	Montreal	−73.57
Seattle	−122.33	Calgary	−114.07
Chicago	−87.63	Houston	−95.37
Boston	−71.06	Dallas	−96.80

What the Tool Does With Your Longitude

Anchored to your device’s time zone, the engine applies two corrections automatically (see True Solar Time explained):

Longitude offset: the gap between your actual longitude and your time zone’s reference meridian, at 4 minutes per degree;
Equation of Time: the seasonal orbital deviation (−14 to +16 minutes).

For example, in San Francisco (−122.42°, Pacific reference meridian −120°): the longitude correction is (−122.42 + 120) × 4 ≈ −10 minutes — when local clocks read 12:00, True Solar Time is about 11:50 (plus the day’s Equation of Time).

Common Questions

Born in China, living in North America — which longitude for today’s fortune? Charts of the present moment use your current location; only natal (BaZi) charts use the birthplace longitude.
What if my phone’s time zone didn’t switch? The device time zone must match where your body is (phones normally handle this automatically) — otherwise the anchor itself is wrong.
Do I subtract an hour for daylight saving? Not for present-moment charts — your device’s time zone already encodes DST and the tool handles it. Only manual conversion of historical birth times needs it: see How DST Affects Your Chart.