A night owl, evening person or simply owl, is a person who tends to stay up until late at night.
The opposite of a night owl is an early bird, a lark as opposed to owl, someone who tends to begin sleeping at a time that is considered early and also wakes early. In several countries, early birds are called "A-people" and night owls are called "B-people." Researchers traditionally use the terms "morningness" and "eveningness" for the two chronotypes.
The term is derived from the primarily nocturnal habits of the owl. Usually, people who are night owls stay awake past midnight and extreme night owls may stay awake until just before or after dawn. Night owls tend to feel most energetic just before they go to sleep at night. Some night owls have a preference or habit for staying up late, or stay up to work the night shift. Night owls who work the day shift often have difficulties adapting to standard day-time working hours.
Owls, like this one in Poland, are often nocturnal.
While it has been suggested that circadian rhythms may change over time, turning lark to owl (or vice versa), evidence for familial patterns of early/late waking would seem to contradict this.
Night owls have often been blamed in the past for unpunctuality or attitude problems. Companies however have begun to learn to increase productivity by respecting body clocks through flexible working; while the Danish "B-Society" of night owls lobbies actively for more workplace flexibility for the post-agricultural world.
Others like British author Hilary Rubinstein would positively celebrate the status of night-owl: "Blessed are the owls, for they shall inherit the mystery and magic of the night."
Discussions and studies about the prevalence of morning, evening, and indifferent or intermediate chronotypes use different criteria and come to different results. Some ask what time people do go to sleep and wake up—others ask what time people would prefer to. A survey of over 400 adults showed approximately 15% morning people, 25% evening people, and 60% intermediates.