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End evening civil twilight (EECT)

Definition End Evening Civil Twilight (EECT) is a military term referring to the time when the sun is 6 degrees below the horizon in the evening, marking the end of twilight. This is often considered the boundary between daylight and darkness. The exact timing of EECT can vary based on geographical location and time of […]


End Evening Civil Twilight (EECT) is a military term referring to the time when the sun is 6 degrees below the horizon in the evening, marking the end of twilight. This is often considered the boundary between daylight and darkness. The exact timing of EECT can vary based on geographical location and time of year.

Key Takeaways

  1. End Evening Civil Twilight (EECT) refers to a specific time of day, more precisely, it relates to the time immediately after sunset, when the residual light takes on a blue spectrum, widely used as a parameter in military operations.
  2. EECT is an important concept because it signifies the transition from daylight operations to night-time operations in the military domain. The effective deployment of personnel and resources can greatly depend on such twilight hours.
  3. The term is crucial for strategic planning and scheduling. It is used to determine the visibility conditions and also significantly impacts the accuracy of various military equipment and operations which rely on natural light.


The military term “End Evening Civil Twilight” (EECT) holds significant importance as it relates to strategic planning of operations. EECT marks the time at which the sun is sufficiently below the horizon such that civil activities can no longer be conducted without the use of artificial lighting.

This coincides with the point in time where the ambient light levels from the sun have decreased to a level comparable to moonlight. As such, military units may use this as a marker for transitioning to night operations, during which different tactics, equipment, and considerations may apply.

For covert or stealth operations, EECT can also provide an ideal window of opportunity because the gradually lengthening shadows and growing darkness improve concealment. Therefore, accurately gauging EECT can directly influence the effectiveness and safety of military personnel during their operations.


End Evening Civil Twilight (EECT) is employed in military operations as a measurement of time, particularly as it relates to operational planning and mission coordination. It signifies the exact moment when the sun has completely set and dusk has transitioned into total dark, signifying the end of evening light availability.

This cyclical natural event can play a critical role in determining the best timing for certain strategic actions, taking advantage of reduced visibility conditions for maneuver or concealment, or assessing the potential value and risks involved in conducting activities under darkness. The purpose of referring to EECT in military operations extends beyond merely acknowledging a shift from day to night.

Strategically, it encompasses the transition to night tactics, which can involve changes in equipment, such as night vision, infrared sensors, or other illumination devices, and tactics, like night-time stealth operations, reconnaissance, or specific offensive or defensive actions. On a situational basis, the calculation of EECT can significantly impact the success of a mission by directly affecting visibility, accuracy, and ultimately, stealth and safety conditions.

Therefore, the precise determination of EECT plays a vital role in military tactics and strategy.

Examples of End evening civil twilight (EECT)

“End Evening Civil Twilight” or EECT is a military term used to describe the time when the sun is 6 degrees below the horizon in the evening. It formally marks the end of the day and the start of the night where possible light changes can have significant impacts on the operations. Here are three examples:

Operation Desert Storm: During Desert Storm in 1991, EECT would have been significant because much of the aerial bombing and ground actions were conducted under the cover of darkness. Understanding when exactly EECT occurred helped coordinate attacks, minimizing the risk of being detected by the enemy and increasing the chances of mission success.

D-Day Invasion during World War II: On the eve of the D-Day invasion, Allied forces needed to understand EECT to coordinate and time the arrival of airborne forces and naval bombardments. Getting troops on the ground and softened up defenses right at or just after EECT would give them the cover of darkness to minimize casualties.

Special Forces Operations: For modern-day Special Forces operations, precise timing is often crucial for success and safety. For instance, the Navy SEAL operation that resulted in the death of Osama bin Laden in 2011 purportedly began at night. Knowing the EECT time would have been critical for planning the helicopter infiltration, when they could have moved under the cover of darkness with less chance of being spotted.

FAQs about End evening civil twilight (EECT)

What is End evening civil twilight (EECT)?

EECT refers to the time of sunset, when the Sun is no longer visible on the horizon. This is an important time for military operations as it marks the transition from daylight to darkness and can affect visibility conditions.

How is EECT used in military operations?

In military operations, EECT is used to plan activities such as night training exercises and missions. It helps the military prepare for changes in visibility and can dictate the timing of certain actions.

How is EECT calculated?

EECT can vary depending on geographic location and time of year. It is usually calculated using astronomical data and local sunset times.

Why is EECT significant in military operations?

EECT is significant in military operations because it affects visibility conditions. The decrease in natural light can have an impact on the effectiveness of certain operations, making it critical to plan activities accordingly.

Related Military Operation Terms

  • Military Twilight Operations
  • Nautical Twilight
  • Astronomical Twilight
  • Civil Twilight
  • Standard Time Zone Offset

Sources for More Information

  • U.S. Army Official Website: This is the official website of the U.S. Army, which contains information on a range of military topics including the term ‘End evening civil twilight (EECT)’.
  • U.S. Navy Official Website: The U.S. Navy’s official website provides articles, updates and thorough information about all Navy practices and terminologies including ‘End evening civil twilight (EECT)’.
  • Time and Date: This site provides extensive data about time zones, daylight saving time, eclipse, etc. Therefore, it’s a great resource to know more about ‘End evening civil twilight (EECT)’.
  • U.S. Naval Observatory (USNO): USNO carries out regular observations of the Sun, Moon, planets, and selected stars, maintaining the ‘Master Clock’ for the United States, and provides astronomical data to the U.S. military and other organizations. This resource could give you a deeper understanding of ‘End evening civil twilight (EECT)’.

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