A node indicates that sunset twilight time is detected/calculated.

Civil twilight is the period when the Sun is below the horizon but its center is less than 6 degrees below. The "Civil Twilight Starts" time is the dawn or civil dawn, with the center of the Sun at exactly 6 degrees below the horizon. Equally, the "Civil Twilight Ends" time is dusk or civil dusk, when the Sun is 6 degrees below the horizon in the evening.

During civil twilight, the sky is still illuminated, and with clear weather it is brightest in the direction of the Sun. The Moon and the brightest stars and planets may be visible. It is usually bright enough for outdoor activities without additional lighting.

Near the equator, where the Sun sets and rises in an almost vertical direction, the civil twilight period can last only 21 minutes, a very fast nightfall compared to the much longer periods at southern and northern latitudes. In regions north of 60°24' N or south of 60°24' S, there will be at least one night when it does not get darker than this.

Technically, the start and end times are when the true geocentric position of the Sun is 96 degrees from the zenith position.

 | Data byte | Description                                                        | 
 | :---------: | -----------                                                        | 
 | 0         | User specified.                                                    | 
 | 1         | Zone for which event applies to (0-255). 255 is all zones.         | 
 | 2         | Sub-zone for which event applies to (0-255). 255 is all sub-zones. | 
