A zeitgaber is part of what we commonly know as the circadian rhythm. It’s an environmental agent or event (such as sunlight) that gives cues for waking and sleeping. When people travel between time zones, a common recommendation for overcoming jet lag is to go to sleep and wake up with the sun. By using these zeitgaber cues, your body will more naturally adjust to the new time zone. Other environmental factors also can be zeitgabers — blue light from a smartphone can disrupt sleep patterns, and melatonin can be a zeitgaber to encourage sleep. The word translates literally from German as “time giver.”