How is Sunrise Calculated: A Comprehensive Explanation

We humans have always been fascinated by nature’s wonders and have always wondered how certain natural phenomena occur. The sunrise is one such phenomenon that has piqued our interest for centuries. It is a beautiful sight that marks the start of a new day, but have you ever wondered how the sunrise is calculated?

In this article, we will go over how the sunrise is calculated as well as the factors that influence it.

What is Sunrise?

Sunrise in Telluride Colorado

Sunrise is the moment when the upper edge of the sun appears above the horizon in the morning. It is also known as the “dawn” or “daybreak” and is one of the most beautiful natural phenomena that can be witnessed. The sunrise occurs due to the rotation of the Earth around its axis, which causes the sun to appear above the horizon in the morning and disappear below it in the evening.

How is Sunrise Calculated?

The calculation of sunrise is based on the position of the sun in relation to the Earth’s horizon. It is influenced by various factors, such as the Earth’s rotation, the sun’s position, the observer’s location, and the time of year. The sunrise calculation involves the use of advanced algorithms and astronomical equations, which take into account all of these factors.

If you’re looking for a mathematical answer NASA defines the UTC time of sunrise using the following formula:

sunrise = 720 – 4*(longitude + hour angle) – equation of time

The Calculation Process

The calculation of sunrise involves the following steps:

  1. Determine the observer’s location: The first step in calculating the sunrise is to determine the observer’s location on Earth. The latitude and longitude of the observer’s location are crucial in determining the sunrise time.
  2. Calculate the solar position: Once the observer’s location is determined, the solar position is calculated based on the time of day and the observer’s location. This involves the use of complex mathematical equations that take into account the Earth’s rotation and the position of the sun in the sky.
  3. Determine the sunrise time: The final step in the calculation of sunrise is to determine the exact time when the sun will appear above the horizon in the morning. This is calculated using the solar position and the observer’s location.

Factors that Influence Sunrise Calculation

Several factors influence the calculation of the sunrise. The most significant factors are:

  1. Earth’s Rotation: The sunrise time varies from one location to another due to the Earth’s rotation. The time difference between two locations is approximately four minutes for every degree of longitude.
  2. The Sun’s Position: The position of the sun in the sky is also a crucial factor that influences the calculation of sunrise. During the summer solstice, the sun rises earlier, while during the winter solstice, it rises later.
  3. Observer’s Location: The observer’s location plays a significant role in determining the sunrise time. The closer the observer is to the equator, the earlier the sunrise, while the further away they are from the equator, the later the sunrise.
  4. Time of Year: The time of year is also an essential factor that influences the calculation of sunrise. The sunrise time varies throughout the year, with the shortest days occurring during the winter solstice and the longest days during the summer solstice.


To summarize, calculating the sunrise is a complex process involving numerous variables. The rotation of the Earth, the position of the sun, the location of the observer, and the time of year all play a role in determining the sunrise time.

To accurately calculate the time of sunrise, advanced algorithms and mathematical equations must be used. We hope that this comprehensive explanation has given you a better understanding of how the sunrise is calculated.

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