If the Earth weren't tilted, there wouldn't be noticeable differences in the amount of sunlight we receive as the Earth travels around the Sun. However, the reasons that Daylight Savings Time (DST) has been adopted by most states (Hawaii and Arizona aren't on DST) have to do more with social affairs rather than astronomy.

Germany first implemented a daylight savings plan in 1915, and England did the same the next year. In 1918 the US put a plan in use whereby the clocks would be advanced one hour in the spring and moved back one hour in the fall. In general, farmers disliked this idea, since they were up with the Sun anyway and were often in their fields until the Sun set. They couldn't see how they would be saving daylight by simply changing the clocks, and they were right - we don't get anymore daylight by resetting our clocks. Because earlier in the century most people still lived on farms, Congress was persuaded by farmers in 1919 to repeal the daylight savings legislation it passed the year before. By mid century more people lived in the cities and suburbs than on farms, and most city dwellers liked the idea of the Sun being up for a few hours after they got home from work. Eventually, there was enough support so that now nearly every state changes to DST during the spring. Clocks are moved ahead on the last Sunday of April and moved back on the last Sunday in October.

The key thing about DST is that we get to use the additional light available in spring and summer during the hours we're awake. If we didn't change to DST and you live in Baltimore, which is about 40 degrees north latitude, in mid June, the Sun would rise about 4:30 and set about 7:30. Since most of us start to get ready for school or work about 6:30 or so, this means that maybe two hours of precious daylight are wasted while were snoozing. By moving the clocks ahead one hour in the spring, the daylight is redistributed so that more of us can take advantage of it by doing things outside on the warm summer evenings.

Of course, this means, since there are no free lunches, we have to set the clocks back in the fall. That precious daylight that we enjoyed in the evening has suddenly disappeared. In most place in the contiguous US, the Sun now sets before 5:30, and in another couple of weeks, it'll set before 5:00! On the other hand, the Sun now rises an hour earlier than it did last week. In Baltimore, for instance, it rises today (Thursday, November 1) at about 6:30, and it's starting to get light at 6:00. So, farmers no longer need a lantern to do most of their morning chores. Also, when you go to work in the morning, the Sun is probably already up to greet you as you leave the house, and if you're heading for school, you no longer have to wait for the bus when it's pitch black.

The dates for the earliest and latest sunrises and sunsets occur near the time, but not exactly on the date of the solstices. When the Northern Hemisphere is tilted toward the Sun, the Sun rises early and sets late (summer). Conversely, when our hemisphere faces away from the sun, the Sun rises late and sets early (winter). The Sun is now positioned directly overhead at noon for people living at 12 degrees south latitude. However, because we change the clocks at the end of October by moving them back one hour, in many places in the US, the time of the latest sunrise occurs at the end of October, between the autumnal equinox and the winter solstice.

The Sun is rising now that we're in standard time at about the same time as it was two months ago when we were in daylight savings time. In early September, though, we didn't have to worry about scraping frost off our windshields. From now through early January, the Sun will continue to rise later and later. By January 10 in St Louis, for example, the Sun will rise at approximately 7:20. After which time, it begins to rise a bit earlier each morning. However, last Saturday, the Sun rose at about 7:22 in St. Louis. So the morning before DST ended (October 27 this year), the Sun rise actually occurred later than it did in early January. In Tampa/St. Petersburg, the Sun rose at 7:37 last Saturday morning, but it'll rise at about 7:22 on January 10. In Baltimore, the Sun won't rise until 7:26 on January 10, but last Saturday, it rose at 7:28. By the way, in Phoenix, Arizona the Sun rose last Saturday at 6:42, and it'll rise in early January at 7:33. As mentioned earlier, Arizona doesn't observe daylight savings time, so residents there don't have to change their clocks.

Here are the Sun rise times for a few other cities: New York City, the Sun rose at 7:20 last Saturday, and in early January, it'll also rise at 7:20; Chicago, the Sun peaked above the horizon at 7:16 on October 27, however, in early January, it won't rise until about 7:18; Seattle, the Sun rose last Saturday at 7:42 and it'll rise on January 8 at 7:50. You can probably begin to see a pattern here.

North of about 40 degrees latitude, the Sun rises later at the start of January than it does at the end of October. The further north one goes, near the time of the winter solstice, the longer the period of darkness. So, when we established daylight savings time, we also inadvertently created a system where the time of the latest Sun rise, for inhabitants living south of 40 degrees north latitude, actually occurs more than two months earlier than it does for those people who live across the northern tier of the US. From the end of October through early January, even though the Sun rises later and later each day every where in the Northern Hemisphere, for those people living south of about the 40 degree parallel, it never quite rises late enough to make up for the 1 hour time change difference.