The Sunrise Sunset Calculator is a free application that lets you find the following timings for either your current location or any given location on the earth:

1) Sunrise and sunset
2) Civil Dawn and Dusk
3) Nautical Dawn and Dusk
4) Astronomical Dawn and Dusk

The computation is done using the formulae at http://www.edwilliams.org/sunrise_sunset_algorithm.htm. Note that since these formulae do not take into account the elevation of the place the computed values may be slightly inaccurate for places much above sea level.

The Sunrise Sunset Calculator also has the following features:

1) It lets you to set alarms at sunrise sunset and any of the above dawn or dusk times.
2) It also lets you set alarms with offsets to any of these time for ex. 10 mins before dusk.
3) It lets you search sun in the sky map.

All of the features currently supported by the app are free.

The web version of the app which does not currently have the alarms and sky map features that are present in the Android app version can be accessed at https://sunrise-sunset.multisocialshare.com/