It was considered desirable for human beings to get up naturally at sunrise and fall asleep when the sun goes down. In recent years, however, life rhythms have shifted to nocturnality due to the increase in the number of 24-hour stores and the constant Internet use. Compared to working adults, junior high school students, and high school students who have a relatively regulated life, university students tend to lead irregular and rhythm-free lives. This study investigated the actual situations of university students’ daily life related to their living hours and examined whether the morning‒night life rhythm was related to their interpersonal relationships. A questionnaire survey was conducted with 184 university students to distinguish whether they were morning or evening people. The Japanese version of Home and Östberg’s morningness‒eveningness questionnaire was used to determine each student’s life rhythm. In addition, the respondents were asked about their time-related daily behaviors, such as wake-up times and bedtime, use of an alarm, frequency of late arrival to classes, physical condition and appetite for 30 minutes after getting up, and their sense of time. The university students’ life rhythms were categorized as 21.7 % morning people, 57.1 % day people, and 21.2 % night people. While 80% of the morning students were satisfied with their current life rhythm, 58% of the night students were not satisfied with their life rhythm. The results of the friendship scale showed that there was no relationship between life rhythm and friendship in boys. In girls, however, some differences were recognized, e.g., morning girls tended to confess their hearts and cherish their relationships with intimate friends, while night girls tended to refuse to be deeply involved with their friends.