Individuals regularly predict the duration of events and tasks in their daily lives, forming plans and allocating time for various activities. However, these predictions are often inaccurate and are susceptible to many factors. This dissertation examined time prediction patterns from a cultural and developmental perspective, which was not comprehensively investigated in the past literature. Chapter 2 considered the effects of reminders of past experiences and the introduction of social consequences on adults’ time estimates for everyday tasks in a cross-cultural context. Asian participants, unlike their European American counterparts, tended to inflate their predictions in response to these factors, as shown in Study 1. Study 2 extended these findings to European American, Asian American, and Chinese college students, with Chinese students showing the most pronounced increase in prediction times. Chapter 3 further compared individuals’ predicted and actual completion times for short tasks, using an anagram task and a visual search task. The findings reinforced that individuals generally overestimate brief task completion times. Moreover, participants consistently predicted longer completion times for subsequent trials than their actual completion times in preceding trials, indicating a pessimism bias. Interestingly, this overestimation increased in later trials, with participants neither becoming more accurate in their time predictions nor shifting from overestimation to underestimation as they gained more experience with the task. A cultural difference emerged in the first study but was not observed in the second study. Asian participants displayed a more cautious approach to time prediction in general compared to their European American counterparts. Nevertheless, the overarching patterns within each cultural group remained similar. While a considerable body of research examines time prediction behaviors in adults, there remains a conspicuous gap in the literature concerning the analogous patterns in children. The final study asked children aged 5 to 10 to predict their completion times for a visual search task. Results showed older children (7-10 years) generally overestimated time requirements, while younger children (5-6 years) didn’t show this tendency. These findings illuminate the developmental trajectory of time prediction and can inform strategies for enhancing it, while also elucidating the developmental origins of adult biases in time prediction.