LONDON (AP) — Jet lag is a problem for many travelers but there are some easy ways to adjust your body clock. It might take planning ahead and getting exposure to sunlight after you land. Scientists define jet lag as the effect on the human body of traveling across different time zones. When we travel to another time zone, it can take our bodies awhile to reset our internal clocks. It's during that adjustment period that we feel tired and sleepy. One expert says to avoid overnight flights if you can and fly during the daytime.