Comedian Mitch Hedberg said, “I used to do drugs. I still do, but I used to, too.”Which illustrates our need for timelines.Hedberg’s gag implies two separate time periods when there’s really just one. Distorting temporal relationships can be engaging and funny in jokes and riveting in movies like “Pulp Fiction” and “Memento,” but usually doesn’t make for clear communication.How many times have you stopped a friend who was yapping away to ask, “Wait. Was that …