App shows illumination data based on location (detected by device or entered by user) and time. The illumination data is available for a single date or for a range of dates.

Data shown:
* Begin Morning Astronomical Twilight (BMAT),
* End Morning Astronomical Twilight (EMAT) / Begin Morning Nautical Twilight (BMNT),
* End Morning Nautical Twilight (EMNT) / Begin Morning Civil Twilight (BMCT),
* End Morning Civil Twilight (EMCT) / Sunrise,
* Midday,
* Begin Evening Civil Twilight (BECT) / Sunset,
* End Evening Civil Twilight (EECT) / Begin Evening Nautical Twilight (BENT),
* End Evening Nautical Twilight (EENT) / Begin Evening Astronomical Twilight (BEAT),
* End Evening Astronomical Twilight (EEAT),
* moon rise,
* moon set, and
* percent lunar illumination.

Data is calculated so app can work in off-line mode.

Features:
* Location in decimal degrees or degrees/minutes/seconds.
* Location can be detected by device, coordinates can be entered manually, or selected on a map.
* Location can be saved and loaded later.
* Times are displayed in local or UTC time.
* Internet connectivity not required (except for Google Maps).