How do FARs define night time?

• A. The time between sunset and sunrise.
• B. The time between the end of evening civil twilight and the beginning of morning civil twilight as published in the American Air Almanac, converted to local time.
• C. 0000 to 0600 local time.
• D. The period when the airplane's navigator can't work.

Answer: (B)

Night in FARs is defined by where the sun sits relative to the horizon, not by a fixed clock time. It lasts from the end of evening civil twilight to the beginning of morning civil twilight, with those boundaries taken from the American Air Almanac and then converted to local time. Civil twilight occurs when the sun is between 0 and 6 degrees below the horizon, so the end of evening civil twilight is after the sun has dropped more than 6 degrees below the horizon after sunset, and the start of morning civil twilight is before sunrise when the sun is already more than 6 degrees below the horizon. Because these times vary by date and location, the exact night period is given in the Almanac for local use. This ensures a consistent standard across different places and times, rather than using sunset-to-sunrise or a fixed clock window.