Getting viewers to watch an evening of programs on traditional over-the-air television networks can be a trying proposition these days, with low-budget niche cable networks chiseling away at the national audience. So the Big Three networks have been trying out a new tactic in the ratings wars: clock manipulation. Rather than ending one program at 7:59 and starting the next one at 8pm, for instance, the network might run the first program a few minutes long, and then immediately start a new show at 8:03, by which time you, the viewer, have already missed the opening of shows on other channels, and are more likely to stick with the network you’re already watching.