In recent years, there has been a notable rise in the development of mobile apps to deliver stress management interventions. However, the prevailing design of most available stress management apps leans towards an emotion-focused coping approach, primarily targeting the regulation of stress-induced negative emotions. Given that the perception of time shortage is a major source of stress among students in higher education, we adopted a problem-focused coping approach that targets tackling student stress via time management. Our work evolved through four main phases. First, we previously conducted a large-scale study involving 502 students, constructing five structural equation models (SEMs) to pinpoint the most effective time management factor in promoting the perception of control over time. Second, based on the findings, we designed and developed a persuasive mobile app (SortOut) to promote effective time management behavior among the target users. Before the development phase, the initial app prototype was evaluated and refined with students (n = 69). In the final phase, this paper focuses on the culmination of our work, wherein we assessed the app’s effectiveness through a 4-week field study involving 34 students. Subsequently, we conducted one-on-one interviews with 11 students to delve into their experiences and feedback. The results revealed that, after using the app, students demonstrated improvement in time management behavior, higher academic self-confidence, and lower stress compared to the baseline. Students in the early and later stages of behavior change (based on the Transtheoretical Model (TTM)) reported similar positive outcomes. Moreover, students perceived the app as straightforward and easy to use; they were not tense or pressured while using the app, which is especially vital for stress management interventions. Thematic analysis showed that the app encouraged organizational thought and behavior and aided students in managing their time and workload, increasing the commitment toward task completion. The study findings suggest that the app helped students engage in effective time management behavior with an improved perception of control over time. Such improved perception is instrumental in promoting student confidence and well-being. Guided by the study findings, we provided actionable design recommendations and future research directions to facilitate the development of impactful persuasive time and stress management interventions.