In ancient times, all Feng Shui Masters used only the "True Solar Time" by using the sundial measurement to base all their Feng Shui calculations and applications like date selection and 4 pillars reading. The "TST" helps us to determine the real "Yang Qi" energy that we receive from the sun. Our Feng Shui society followed the clock time only during the last century when the western world invented the "clock time" although it bears no relationship to the real Yang Qi from the sun energy.
Sundials tell the "sun time" while clocks and watches tell the "clock time". They should be used appropriately according to their specific purpose.
"Solar time" or "Sun time" is anchored around the idea that when the sun reaches its highest point when it crosses the meridian or the most Yang Qi, it is noon and the next day when the sun crosses the meridian, it will be noon again. The time which has elapsed between successive noons is sometimes more and sometimes less than 24 hours of a clock time. In the middle months of the year, the length of the day is quite close to 24 hours, but around the 1st of September the days are only some 23 hours, 59 minutes and 41 seconds long while around Christmas, the days are 24 hours and 31 seconds long.
"Clock time" is anchored around the idea that each day is exactly 24 hours long. This is not actually true, but it is obviously much more convenient to have a "mean sun" which takes exactly 24 hours for each day, since it means that mechanical clocks and watches, and, more recently, electronic ones can be made to measure these exactly equal time intervals.
Please download the full article in pdf file: Time Adjustments to "True Solar Time"
