The tilt of the earth on its axis and  our location north of the equator  result in a sun path that changes throughout the year.  The sun is at its highest point at noon on the Summer Solstice, or June 21st.

Most photovoltaic and solar hot water systems are stationary, and having unobstructed solar access between the hours of 9AM and 3PM is ideal.
Tracking systems usually follow the sun path from east to west during the day, and are seasonally adjusted for altitude angle.