Aging and physical inactivity are global concerns that contribute to heightened medical costs and welfare demands. Older adults can benefit much from physical activity (PA) participation, but unfortunately they are the least active population segment. More research on PA promotion among older adults is warranted. One major research gap is that, while distal health outcomes are usually the focus in promotion, older adults are characterized by their restricted future time perspective (FTP). Thus, older adults might not benefit from such future-based promotion. Recent studies have demonstrated the importance of immediate rewards in the amount of effort spent in PA as well as past and future PA participation. This proposed project aims to examine whether and how older and younger adults benefit from immediate effects of PA and whether present-based strategies are more effective in promoting PA than future-based strategies and/or a control condition among older adults. Study 1 aims to examine 1) whether age moderates the effects of immediate benefits on future PA and 2) whether FTP and health consciousness mediate the proposed age moderation. Using a prospective survey study, 190 older and 190 younger adults will report the importance of immediate and delayed rewards of PA, PA intention, FTP, health consciousness, and demographic and health factors at baseline and their PA behavior after 2 weeks. Structural equation models will be used to test the moderating effect of age on the relationship between immediate rewards and subsequent PA. A mediated moderation analysis will be conducted to examine whether FTP and health consciousness can explain the age moderation. Study 2 aims to examine 1) whether present-based strategies are more effective than future-based strategies or a control condition in promoting PA among older adults, 2) whether treatment acceptability is higher for those using present-based strategies than those in the other conditions, 3) whether future-based strategies induce more psychological distress than present-based strategies, and 4) whether individuals’ FTP moderates the effects of time-based strategies on PA participation. Using a three-arm experimental design, 198 older adults will be randomly assigned to one of the three conditions including present-based strategies, future-based strategies, and a control condition. After the manipulation, the participants will wear an accelerometer for 2 weeks to objectively measure their PA levels. Differences in PA participation, treatment acceptability, and psychological distress among the experimental conditions will be tested in separate sets of ANCOVA/MANOVA. The moderating effects will be tested using multiple regression analyses.