how long does the twilight last
Twilight is arbitrarily divided into three increments. The period when the Sun is 6 degrees or less below the horizon is called civil twilight . Further inspection of figures 7, 8, and 9 reveals that the time for the Sun to reach these twilight angles differs at different seasons. At the equator, the evening Sun reaches the position ending civil twilight in only 23 minutes. In Hawai'i, civil twilight lasts 27 minutes in winter and 28 minutes in summer. At 45 degrees latitude the same period is 35 minutes in winter and 37 minutes in summer.
The more popular concept of twilight more nearly matches the period of nautical twilight, and the effect of latitude is more pronounced for this period. In Hawai'i, nautical twilight ends 52 minutes after sunset in winter and 55 minutes after sunset in summer. At 45 degrees latitude, the corresponding periods are 73 minutes in winter and 85 minutes in summer. the longer hours of twilight at higher latitudes contribute to the acceptability of daylight saving time.