In Canada, night is defined as

• A. the start of evening civil twilight to the start of the morning civil twilight
• B. the end of evening civil twilight to the end of the morning civil twilight
• C. the start of evening civil twilight to the end of the morning civil twilight
• D. the end of evening civil twilight to the start of the morning civil twilight

Answer: (D)

Night is defined by the sun’s angle below the horizon using civil twilight boundaries. Civil twilight lasts when the sun is between 0 and 6 degrees below the horizon. Night begins after evening civil twilight ends (that is, when the sun is 6 degrees below the horizon in the evening) and ends before morning civil twilight begins (when the sun is 6 degrees below the horizon in the morning). So the night interval runs from the end of evening civil twilight to the start of morning civil twilight. This frame keeps the definition consistent across Canada’s different latitudes and seasons, rather than tying night to fixed clock times.