# Solar Time

Until the late 19th century most people used local solar time so that noon was when the sun was directly overhead, and each town had its own definition. Transport was slow, so it did not matter that the time in a town miles away varied by a few minutes. The advent of railways necessitated more accurate time keeping and time zones were introduced to keep an entire region on the same time1恒大彩票网址是多少. Time zones follow political boundaries so that local time may be up to 2 hours different from solar time.

### Local Solar Time (LST) and Local Time (LT)

Twelve noon local solar time (LST) is defined as when the sun is highest in the sky. Local time (LT) usually varies from LST because of the eccentricity of the Earth's orbit, and because of human adjustments such as time zones and daylight saving.

### Local Standard Time Meridian (LSTM)

The Local Standard Time Meridian (LSTM) is a reference meridian used for a particular time zone and is similar to the Prime Meridian, which is used for Greenwich Mean Time. The LSTM is illustrated below.

The (LSTM) is calculated according to the equation:

$LSTM=150∆TUTC$

where ΔTUTC is the difference of the Local Time (LT) from Universal Coordinated Time (UTC) in hours. ΔTUTC is also equal to the time zone. 15°= 360°/24 hours. For instance, Sydney Australia is UTC +10 so the Local Standard Time Meridian is 150 °E. Phoenix, USA is UTC -7 so the LSTM is 105 °W

### Equation of Time (EoT)

The equation of time (EoT) (in minutes) is an empirical equation that corrects for the eccentricity of the Earth's orbit and the Earth's axial tilt. An approximation 2 accurate to within ½ minute is:

$EoT=9.87sin2B-7.53cos⁡B-1.5sin⁡B$

where

in degrees and d恒大彩票网址是多少 is the number of days since the start of the year. The time correction EoT is plotted in the figure below.

### Hour Angle (HRA)

The Hour Angle converts the local solar time (LST) into the number of degrees which the sun moves across the sky. By definition, the Hour Angle is 0° at solar noon. Since the Earth rotates 15° per hour, each hour away from solar noon corresponds to an angular motion of the sun in the sky of 15°. In the morning the hour angle is negative, in the afternoon the hour angle is positive.

### Local Time to Local Solar Time Calculator

Enter a location above to get its longitude and time zone. Once the time zone is determined, the latitude is not needed when calculating the local solar time. The longitude and time zone can also be entered directly without having to use the lookup. Standard time is used and there is no correction for Daylight Savings.

Local Solar Time

###### Results

Equation of Time X minutes.
Local Standard Time Meridian: X °
Time Correction: X minutes
Hour Angle X °
Local Solar Time X (HH:MM)
latitude X恒大彩票网址是多少 ° (not needed)