The best time to water is early morning. Water scheduling also depends on your specific soils and factors such as amount of shade, amount of mulch on garden that will influence amount of soil moisture retained in soil. Many agencies got together and produced a brochure on proper water of lawns called Residential Watering Guide specific to each county. For Salt Lake County check out this link http://www.conservewater.utah.gov/agency/materials/guide/SaltLake.pdf
If you have any other questions, you can check out our Extension website for Salt Lake County under horticulture (use right hand navigation bar) and link to other USU publications http://extension.usu.edu/saltlake/htm/horticulture