Where to Find the City Longitude of Your Birthplace
We have 24 hours a day. The clock time corresponds to the position of the Sun in the sky. Chinese horoscope calendar adopts the cycles of the Sun. Therefore, our birth time for Chinese horoscopes needs accurate solar time. Our clocks and computers display the time of our time zones. We have 24 time zones and 24 hours a day. Therefore, one timezone covers 15 minutes long. If your birthplace is the city on the boundary of two different time zones, then your actual birth time has about 7 minutes difference from the standard time.
Chinese astrological hour unit in the calendar is two hours long. Usually, we don't need the city's longitude to calculate the exact birth time to have a correct Chinese horoscope birth chart. However, if your birth hour is around 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, and 23 o'clock, then you need to use the city longitude of the birthplace to find your correct solar time. Also, if you were born on the boundary of the Chinese astrological boundary or around midnight, then the city's longitude and time zone are critical factors to find your correct birth time.
To find your city longitude is to click the Go button below, then type your birth town to find the city longitude. If the city longitude is 128w23, then use 128.23 as the west longitude in the Chinese calendar screen with a negative sign. If the city longitude is 118e36, then use 118.36 as the east longitude.
Local Mean Time - Longitude Time Calculation
To build a correct Chinese Horoscope birth chart is required accurate birth time. People record their birth time by the clock. The clock time is the time of timezone, which is called mean solar time.
We have 24 time zones around the world. One time zone is one hour long. The circle of the globe is 360 degrees. Therefore, a time zone is 15 degrees. One degree is 4 minutes. For example, US Pacific Timezone covers 15 degrees of longitude from 112.5W to 127.5W. The Pacific Standard Time (PST) is the clock time of west longitude 120 degrees. The longitude time inside the PST is called the local mean time. You can see our examples to adjust your birth time using the city's longitude and time zone.
If a person were born at the boundary of Chinese astrological units, then we need to convert the birth time to the true solar time, which is the sundial time, using the Equation of Time.
How to Adjust Birth Time using TimeZone and City Longitude
How to Calculate True Solar Time, Sundial Time
Daylight Saving Time, USA, China, Taiwan, Hong Kong, Singapore
By Master Allen Tsai on January 12, 2022