As if night flying isn't confusing enough!

There are three main situations in aviation that require a knowledge of when night occurs:

1. Logging time for training and experience for ratings
2. Currency in takeoffs and Landings
3. Safety Lighting (Position and AntiCollision Lights)

Of course, each uses a different definition of Night. Training and experience use 14 CFR 1.1. Currency in takeoffs and landings uses 14 CFR 61.57, and Safety lighting uses 14 CFR 91.209.

Sunset is different from other twilight calculators because it is indepedent of an internet or cell phone connection. It works well in an aircraft at altitude, or at a remote airstrip without connecting to a server like the Naval Observatory.

When Sunset starts, it displays the sunrise and sunset data for the your present GPS location, assuming the location services are present and enabled in your device's Settings. You easily can change the location and the date for which the twilight calculations are made.

The calculated information is displayed in graphic form as a 24 hour clock face. The yellow displays the daylight hours, the red arcs are the periods of twilight between civil sunrise and standard sunrise, and between standard sunset and civil sunset. The black arc is night time which encompasses Nautical twilight, but that is another story. The yellow ball is the sun indicating the time of day.

The results are also provided as text inside the clock. The top row of times are the standard sunrise and sunset times. The second line lists the civil twilight rise and set times. The next line down reports the time zone at the location for which the calculations were performed (see Changing Location below). If the selected location is outside the timezone where the app is physically located, the app will calculate the present time of day at the location and its timezone as well as the appropriate twilight times. The fourth line is the current time at the selected location. The bottom line is the number of hours and minutes until the next civil twilight (rise or set as appopriate).

Changing Location. This app can calculate the sunrise and set times all over the world. It has three different ways to set a location: Current actual GPS, Any listed airport (worldwide), or when connected to the internet by entering a street address which can be converted to a latitude and longitude.

Changing Date. The app will normally compute the sunrise and set data for the current date and time of day. However, it can also compute the data for arbitrary dates in the past and future using a standard Date Picker interface.