Published: 2007-03-24 08:37:47
Updated: 2007-03-24 08:37:47
Posted March 24, 2007
By Glenn Perry
MIKE MOSS SAYS: Glenn, That would refer to the time at which the center of the sun's disk has fallen to 6 degrees of arc below the horizon after sunset. For more details, see the earlier Q&A at
or you can access that answer by typing "civil twilight" into the search box at the upper right corner of any page on our site.