Nowadays, obtaining and gaining the control of energy sources are difficult and costly. Besides, most of the wars are due to energy aspects. Therefore, energy saving has now become very important for all countries in the world. Furthermore, the energy management and saving matters are adopted as fundamental policies by the governments as well. Some projects based on energy efficiency are even supported by the nonprofit foundations. Additionally, countries are exploring new energy sources and finding new techniques in using energy thrifty. The streetlights or outdoor lighting items are used up a plenty of energy in vain in some part of the day such as twilight duration because of using conventional photocell relays. Changing in the sunrise and the sunset times during the year, profiting duration from the daylight is different for each day. As the photocell relays have different inner impedance versus daylight, and the weather may be cloudy or clear, they can be turned-on early and can be turned-off lately. Besides, these relays are not so sensitive to twilight. Therefore, the amount of energy wasted during the year is going to be considerable. The duration of the consumption in vain is one hour per day at least. However, in case of using astronomical time relays, since the sunrise and the sunset times related to different time zone can be calculated during the year, all of the streetlights can be controlled by different offset time and can be saved respectable amount of energy per year. In this study, the importance of using the astronomical relays for outdoor lighting for energy saving and efficiency is discussed. The operating principal of these relays is analyzed by purposed method and compared with that of NOAA. An implementation of an astronomical time relay for Denizli City in Turkey is selected as a case study. It was proved that the energy consumption in vain one hour per day during the year is remarkable amount in the selected plot application area. © 2009 Praise Worthy Prize S.r.l.