Why was it difficult to tell the time of day?
The story is set on the tundra. The tundra ground is covered by a thin, soggy layer of small plants, moss and grass. Beneath the top soil layer is the permafrost, a layer of permanently frozen soil. It is so hard no roots can penetrate it and no water can seep through it. It is very unforgiving.
The tundra is a very important part of the story, that contributes to plot. There is no wood to make a fire with, so Julie gathers dried caribou droppings. The landscape is flat with no identifiable landmarks.
Julie camps in a small depression to hide from the wind. Whenever she moves from an area, she has to mark her path so she can find her way back.
The arctic summer is only two or three months. At this time, the sun never sets. It is impossible to know what time it is. Its movement cannot be used to point to either east or west.
Julie cannot know for sure autumn, when migrating birds fly south, and winter, when the pole star can be seen in the sky--all of this she must do before she can find her way through the wilderness.