Comparing the behavior of people living in eastern and western Germany, [a recent study in Current Biology] shows that the average mid-sleep moment varies by four minutes for each degree of longitude. The consequence is that the mid-sleep moment for Germans who live near the western border happens 36 minutes after the midsleep moment of Germans who live along the eastern border.
This would seem to make sense, given that the sun takes exactly four minutes to move by each degree of longitude. The issue, though, is that time zones are not strictly based on this path. The time zone in eastern and western Germany is in fact the same. As a consequence, people who live on the western edge of a time zone suffer from sleep deprivation. The social jet leg is the exhaustion produced by this gap, and might lead to chronic disorders.
More Dish on social jet lag here.
(Chart via Maria Popova)