Thanks to the development of digital technology, short-videos have become fully integrated into users' daily lives. Time, as an intangible yet important environmental variable, subtly influences individuals' cognition and behavior in various ways. Among the existing studies on short-video platforms, there has been limited focus on the impact of temporal landmarks on social media users' behavior and preferences. To address this gap, this paper examines how beginning or ending temporal landmarks in short-videos activate a sense of starting or finishing within a social media context. It explores the mechanisms of user preferences for personal branding under different temporal perceptions and further examines the boundary role of users' personal traits. The results show that the main effects of temporal landmarks on personal brand preferences, as well as the mediating role of attributional needs and uniqueness needs and the moderating role of self-construal, are significant. Specifically, for users with independent self-construal, those activated by beginning temporal landmarks show a higher preference for competence-based personal brands
for users with interdependent self-construal, those in scenarios with ending temporal landmarks exhibit a stronger preference for warmth-based personal brands. This paper enriches research on user behavior related to temporal landmarks in social media, expands the applicability of the stereotype content model in personal branding, and provides suggestions for short-video social media platforms to attract, convert, and monetize user traffic. It also offers marketing insights for businesses on arranging activities according to consumer traits and temporal factors.