If you're an advertiser, the best time for your commercial to air on broadcast networks is between 9 15 p.m. and 9 30 p.m. That's when most people are watching, Nielsen Media Research said on Tuesday. The worst time for your commercial to air is between 10 45 p.m. and 11 00 p.m. That's when the fewest people are watching, with many heading off to bed. Nielsen pointed out that while there is virtually no difference in those numbers between men and women, there is a decided difference when it comes to age. The number of viewers in the 18-49 demographic, which constitutes the most sought-after segment of the viewing audience, surges in the 9 45 p.m. to 10 00 p.m. period, while the fewest number watch at the beginning of primetime, 8 00 p.m. to 8 15 p.m.