Which term is used to denote a 24-hour period starting at 0001 local time?

• A. Air Traffic Control
• B. Calendar Day
• C. Comat
• D. Altitude

Answer: (B)

Think about how daily time is tracked in aviation. A calendar day is the 24-hour span that begins at 0001 local time and ends at 2400 local time on the same date. This framing is used for daily records, crew duty reporting, and scheduling because it aligns with the local date. The other terms refer to things rather than a time span: air traffic control is the service that manages aircraft, altitude is vertical distance, and the remaining term isn’t a standard term for a day. So the term that denotes a 24-hour period starting at 0001 local time is calendar day.