What is the length of the day in Chico on the Summer Solstice? The latitude of Chico is 39.73o and the earth's rotational axis is inclined at 23.5o towards the sun. Hint: Chico's daily path is a circle with a portion of its circumference in the night's darkness. View the orbit from the side (in cross section) and then also from the top (in cross section) and that will give you enough information to deduce just what fraction that dark portion must be of the whole journey. Since once around represents 24 hours you will know what fraction of that time must be dark.