True sunTime, foreign name: apparent solar time, divided into 24 true solar hours.This time system is called true solar time.True solar time is also called apparent solar time, which is called apparent time for short.True solar timeHour angleAdd 12 hours.That is, true solar time=Flat sunHour+true mean solar time difference.Direct sunlightThe longitude line of the time zone is 12:00.The time increases by 4 minutes for each degree of rotation of the earth.
The center of the solar apparent circle goes up to the midheaven twice in successiontime intervalbe calledTrue solar day。The true sun day is divided into 24 true sun hours.This time system is called true solar time.Therefore, in order to be consistent with people's daily habits, the true solar time is defined as:Hour angleAdd 12 hours.Since the true solar time is obtained by observing the center of the solar apparent circle, it is also called the apparent solar time, which is called the apparent solar time for short.That is, true solar time=Flat solar time+TrueFlat sunJet lag.
Timing method
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The true solar hour is centered on the true solar viewing circleHour angleThe starting point is the true sun rising to the sky, while in our daily life, the starting point is midnight（Lower Midheaven）, the difference is exactly 12 hours.
computing method
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reallysunlightCalculation method of peaceful solar time difference:[1]
Where Δ t is the time difference;θ is the solar angle (radian);
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N is the product day,[2]Annual product dayIt refers to the continuous calculation method used only in one year. It refers to the number of days from January 1 of the current year.For example, January 1 of each year is the first day, February 1 is the 32nd day, and so on.December 31 of a normal year is the 365th day, and December 31 of a leap year is the 366th day.
N0 is the standard year,
N0=K+0.2422 × (year - standard year)-INT(0.25 × (year - standard year));
