Final answer:
The narrator usually sleeps at night, complying with the human diurnal nature and circadian rhythm that induces sleepiness after dark and awake states during daylight.
Step-by-step explanation:
The narrator typically sleeps at night, as suggested by their diurnal nature mentioned in the contextual information provided. Humans generally feel sleepy after dark due to circadian rhythms, which are the daily cycles of behavior regulated by environmental cues like light and darkness. While the exact time of sleep was not specified in the provided passages, it is indicated that the narrator awakes to sunlight, implying a sleep cycle that coincides with nighttime hours as expected for diurnal creatures.