An almanac providing basic sun and moon data can be a useful addition to sites that include astronomy, religious, education, energy-related, weather, or astrology information. Sites devoted to a range of outdoor activities, from night photography to fishing, can also benefit from adding an almanac.
PHP V5 includes sunrise and sunset functions to make the job of adding sunrise/sunset data easier. However, calculating the time of the rising and setting of the moon is more complex. The problems of calculating moonrise and moonset for a location - such as parallax, refraction, and accounting for days when there is either no moonrise or moonset - have been given exhaustive treatment elsewhere (just do a Google search on moonrise calculations.)
