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Daylight and Darkness Graphs

“Night” is that period between the end of evening civil twilight and the beginning of morning civil twilight.

For all intents and purposes, first light should be construed as the beginning of civil twilight (Beginning of Daylight), and last light as the end of civil twilight (End of Daylight). The terms “sunrise” and “sunset” have no relevance when calculating daylight operating times for the VFR pilot.

To compute the beginning or end of daylight using the graphs contained in this section:

  1. enter the top or bottom of the scale at the appropriate date;
  2. move vertically up or down to the curve for the latitude of the place concerned (interpolating for intermediate latitudes if necessary);
  3. move horizontally to the left or right and read local mean time on the vertical scale at the side;