As always, dates of the year run vertically down the side, and time of night runs horizontally. Each curved or slanting line tells the time of night when an event happens throughout the year. The left edge represents the time of sunset, and the right edge marks sunrise. Another difference is the length of twilight. This has to do not with the change in hemisphere but the difference between being 30 or 50 from the equator.
Night falls fast at low latitudes.
Farther from the equator, twilight is always more prolonged. This effect is greatest around the summer solstice. Farther north at Arctic latitudes, the Sun itself never sets around these dates. The territory where this occurs is bounded by the Arctic Circle. Other effects show up on closer looking.