A crossover trial of 27 older adults with insomnia found that morning exercise (10-11 AM) shifted sleep midpoint 20 minutes earlier compared to evening exercise (7:30-8:30 PM), though both timing approaches reduced insomnia severity scores by approximately 2-2.5 points. The study used objective sleep monitoring and found no differences in sleep duration, efficiency, or subjective quality between morning versus evening physical activity sessions. Exploratory analysis suggested late chronotypes—people naturally inclined toward later bedtimes—may benefit more from morning exercise for insomnia improvement. This preprint awaiting peer review adds nuanced evidence to the ongoing debate about optimal exercise timing for sleep health. While previous observational studies hinted at timing effects, this controlled intervention provides modest but measurable data. The 20-minute sleep shift, though statistically significant, represents a relatively small practical change. The finding that both exercise timings improved insomnia symptoms reinforces that consistency in physical activity matters more than perfect timing for most older adults. However, the small sample size and short intervention period limit broader conclusions about long-term benefits or personalized timing strategies.