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Brian Snyder / Reuters
Peter Shugrue checks four custom-made clocks, destined for installation in Kansas City, Mo, at the Electric Time Company factory in Medfield, Mass. Daylight saving time begins in the United States at 2 a.m. Sunday.
It's that time of year, when most Americans lose an hour's sleep setting their clocks ahead. (Remember? Spring forward, fall back.) So here are answers to questions about the time switch and about sleep.
In most of the United States, we'll be moving our clocks ahead for daylight saving time in the wee hours of Sunday morning. The official switch comes at 2 a.m. Sunday, which instantly becomes 3 a.m. Most people, however, move their clocks ahead just before going to bed Saturday night or just after getting up Sunday morning.
The day of the big switch used to be the first Sunday of April, but in 2005, Congress changed the rule to make it the second Sunday in March, as an energy-saving measure.
What's the rationale?
As the year progresses toward the June solstice, the Northern Hemisphere gets longer periods of sunlight. Timekeepers came up with daylight saving time — or summer time, as it’s known in other parts of the world — to shift some of that extra sun time from the early morning (when timekeepers need their shut-eye) to the evening (when they play softball).
The idea is that having the extra evening sunlight will cut down on the demand for lighting, and hence cut down on electricity consumption — and that few people will miss having it a little darker at, say, 6 o'clock in the morning. At least that's how the theory goes.
Who's in on the switch?
Not everybody goes along with the plan. Arizona sticks with Mountain Standard Time, which turns out to be the same as Pacific Daylight Time. (The Navajo Nation, however, goes along with the summertime switch.) Hawaii and U.S. possessions such as American Samoa, Guam, Puerto Rico and the Virgin Islands are also staying on standard time.
Most European countries don't switch to summer time until the last weekend in March. That means the usual time difference will be out of sync for three weeks. For example, when it's noon in New York, it'll be 4 p.m. in London. But starting March 31, the five-hour difference between the two cities' clocks will be back in force.
Some countries in the Southern Hemisphere move their clocks back an hour at this time of year. In Brazil, for example, the switch from daylight saving time to standard time took place in mid-February.
How can we cope?
If you’re in the “spring forward” mode, don’t lose any sleep over the hour you’re losing. But do try to get back into your regular sleep routine. Rosalind Cartwright, a sleep expert at Rush Medical Center in Chicago, says that if you lose too much sleep, even a couple of hours for just two or three days, your immune system will suffer and you'll be more susceptible to colds and viral infections.
A couple of small-scale studies have suggested that heart attack rates go up during the switch to daylight saving time, perhaps because of the sleep-cycle disruption. But the evidence is too meager to make a solid connection to that issue or other purported health effects of the time change.
Generally speaking, if you get to sleep too late, or get up too early, your body will find a way to get the deep sleep it needs for rest. But Cartwright says you lose the stage of sleep during which you dream, which is important for mood. Which explains why you might feel groggy and grumpy after we "spring forward" to daylight saving time.
More about the time changeover:
- Tips to combat daylight saving time fatigue
- PhotoBlog: US gets set to 'spring forward'
- How daylight saving time got started
- Daylight saving time's the time to check smoke alarms
David Ropeik is a consultant and author specializing in risk perception and risk communication. Alan Boyle is NBCNews.com's science editor. This is an updated version of a report originally published in March 2000.
Leave a Comment:
Energy saving measure. Right.
What do people do in the modern mobile world we live in with that extra hour of daylight in the evening?
They drive to the store, shop, movies, lake, go boating, play golf, restaurant, etc. So more gas is used. Then there is the extra electricity to light, cool or heat those places everyone goes to.
Does anyone REALLY think any energy is saved?
I bet it was the outdoor, entertainment, and restaurant industries that lobbied Congress to extend daylight savings time.
Not only are we not saving energy we aren't saving any money either.
"...heart attack rates go up during the switch to daylight saving time, perhaps because of the sleep-cycle disruption."
...or perhaps with the frustration with the underlying laziness of the perpetrators who can't get out of bed.
Economykiller,
And lets think about homes: w/ more personal electronics, large screen tvs.
More businesses open 24/7. For 2-3 weeks in the a.m. lights are needed.
We dont save energy, money or time. Does anyone save time? Where do you keep it?
One of the biggest lobbys pushing for the recent extension was the Charcoal manufacturers. The more daylight left when people get home the more they cook out. What you said was true about people driving more etc. Energy savings are probably nonexistant.
The only reason why george king ordered Daylight Savings Time moved was to please his buddies in the Big Wig Retail Industry. Many Retail believed having Daylight Savings start when THEY wanted it to would bring back the dollars and make them richer. well it hasn't.
Hopefully there will be a President in the Future who will reverse or impeach all the awful laws, decisions and rules leftover from george King. One of those awful decisions resulted in the appointment Supreme Court Chief Judicial Activist John Roberts whom needs to be impeached and removed from Office legally. The other was extending Daylight Savings time.
And thats my Opinion
President Nixon kept us on daylight savings time for the full year once. We did not have to switch back in the fall that year of leap forward the following spring. It made sense and it gave us longer evenings that winter.
sh!t, some people would b!tch about the sun rising in the east if they had an opportunity for an argument and to have an opinion on what others collectively accept as an American way of life.
@Gimme ... The fact that that the sun rises in the east is a plot by east coast liberals to enable them to get their welfare checks delivered before the rest of the country.
I hate it.
I ALWAYS know what time it is, w/o looking at my watch . . . until they start screwing around with the clocks.
PICK SOMETHING. STICK WITH IT. DON'T KEEP SWITCHING BACK & FORTH.
PLEASE.
:-)
This spring forward and fall backward stuff is Neandethal. Let’s come into the 21st century and be liberally sophisticated. It's global warming forward and climate change backward.
Actually, it was the environmentalist wackos who lobbied for it. And, as we all know, it's not what you do or whether it works, it's that you do something. Doing something, anything, shows you care. If you don't do anything or question the wisdom of what that something is, then you evil and you don't care. Just a fact of life. Personally, I prefer to stay on the Summer time. I love being outside as late as possible after work and don't care if I wake up in the dark or the light.
I LOVE daylight savings time!
When told the reason for daylight saving time the old Indian said…
‘Only a white man would believe that you could cut a foot off the top of a blanket and sew it to the bottom of a blanket and have a longer blanket.’
The only use daylight savings has in our modern world is to cause everyone to lose an hour of precious sleep.
If you go to bed an hour early, you don't.
I hate daylight savings time.
I LOVE it!
I love the extra hour of daylight. Get outside, folks!
If anyone claims that a one hour clock change twice a year physically affects them, they should work rotating shifts, as I did. Do they go to bed, and rise at the same times every day? Of course not.
How about doing as China does, and have one time zone?
My wife is thrilled at the onset of gardening season, the extra hour of light in the evening.
I'm with you, Spike. An hour of daylight in the morning does nothing for me, but I love having extra daylight when I leave work.
Yes an extra hour of sunlight. It will still be sunny at 10pm here this summer. That is more than an extra hour. Thanks Mitch Daniels, the worst Governor Indiana has ever had.
Japan does not have daylight saving time. In June it is broad daylight at 4:30am and dark by 7:30pm. No thanks.
I wish they'd pick one or the other AND LEAVE IT! I do not transition well. I prefer standard time, but will be happy if I never have to fall back or spring forward again.
Bongoman,I agree with you.
I quit changing my clocks years ago.Can't have the man ruling me like that-besides, it's not like we actually have any more daylight hours in the day.Spring forward & stay there.
I agree Bongoman, split the difference (forward or back half an hour) and then leave it alone!!
A stupid, annoying and wasteful twice a year ritual I hate, too.
So raging bull, do you set your TV's and computers etc. back an hour once they automatically switch?
Obviously I don't understand HTML code placement either!
Yea, but the avathing is a riot.
I hate standard time!!!
Crap, more crap from people who have nothing better to do. Except squabble with each other.
I believe that there are also some studies that have shown there are more motor vehicle accidents the Monday after a change to daylight savings time. This is because it takes several days for us to adjust to the hour change. Thus, I wonder why they don't make the change Saturday morning, rather than Sunday, to allow more time for us to adjust. Yes, know I know it screws up people who work on Saturday, but these days, a lot of stores are open 7 days a week...
Author has no business writing about something he clearly knows nothing about. Dreaming occurs in Stage 5 sleep, not in light sleep as author describes. Search on "sleep stages" and you will see. Most people with untreated sleep apnea report rarely or never dreaming because they don't get into deep enough sleep before having an apnea.
I've revised the item to make it clearer that Cartwright is the one who's talking about the kind of sleep that's lost. Also, although she referred to REM sleep as a light stage of sleep, I've changed the reference to avoid confusing REM sleep with Stage 1 sleep, which is often called "light sleep." But I don't think it's true that REM sleep is deep sleep. In fact, it's said to be very similar to the waking state. Stage 4 sleep is more appropriately called "deep sleep," and Cartwright made reference to that stage as well. The Flash interactive attached to the more or less original version of this story helps folks sort out the various stages of sleep:
http://www.nbcnews.com/id/3077304/ns/technology_and_science-science/
Energy savings in exchange for losing time.......... umm i prefer having the extra time thank you.
What have you actually lost? There is absolutely no loss of time involved in this. The clock simply points to a different place.
I am with the Daylight Savings haters - my body never seems to adjust to the phony time - and now I have to deal with it for the majority of the year. Just about the time that getting up in the morning gets easier, they slam us back to having to get up in the dark. And why doesn't anyone mention that in the fall, children are going to their bus stops or walking to school in the DARK?? Yeah, that sounds like a great idea. The whole concept of saving energy is a myth - it doesn't save a penny.
"Phony time"? What is "real" time? Our time zones are artificial creations. It is all "phony" time.
And just why does the US insist on changing daylight savings time earlier in the spring and later in the fall than every other nation in the world? Such arrogance.
I don't know if it's arrogance, but it's certainly annoying to have two brief periods a year when all my European collaborators are five hours ahead of me instead of six. There are always a few people who end up missing a telecon.
Um, Canada?
Well, Richard, someone has to be first.
I guess because we can.
We should do something just because someone else is doing it? What's the logic there?
This article is supposed be about the science of day light savings? OMG we are so doomed. I think those timekeepers were marketing folks who were trying to get people to shop more.
It has no effect on me. But I think it's possibly the dumbest ritual come up with by our "leaders". It serves no actual or practical purpose.
.
I wish it was DST all year around.
.
Setting the clocks back in the autumn is the silly part.
.
I prefer Daylight Saving, as I don't get home from work until 5:30. That gives me a few hours to play outside in the yard and garden beds. I mow, weedeat, pick the daily vetgetables, play with the dogs, and mess with the koi pond. I get exercise and have a nice looking yard and healthier dinners for my efforts. It's more fun and it's not like there is ever anything worth watching on TV. I'd prefer DST year around myself.
An alternative would be to restructure our work days to start and end an hour earlier. Same effect, but no messing around with timekeeping systems.
It's ironic that the high-school kids, who are awful at getting up early, are the ones whose days go from 7 to 3.
We should revert to the way of the ancients: work when it is light; drink when it is dark.....or something like that!!!
I heard most of AZ. doesn't do this,it seems like it would mess things up for the other states. I wonder?
I don't know if it is still the case, but parts of Indiana didn't change, either. Easy enough to work around.
Arizona doesn't change. Woke up today feeling, well, the same. Oh, and it's sunny again today. I could rant about the extreme politics here but that would ruin this uplifting conversation.
Lived in AZ for 13 years, and I missed the time change EVERY year...
Being a farmer, I assure you we do not look at clocks.....sunup to sundown...half of the time I could not tell you what day of the week it is.............
That's nice to live that way,I envy you.
My mother used to find out what day of the week it was by picking up the paper on the front lawn.
For me I wish we would stay on daylight savings time year round. I enjoy the extra daylight in the evening.
It's called "Daylight Saving Time" not "Daylight Savings Time" (there is no "s" at the end of the word "Saving").
Wow, excuse me, I did not know the spelling police were still up. Of course I should have that you probably don't make any mistakes in your typing.
Nelson, don't be a dick. People have been misusing the name for so long that it's annoying. Every year the mouth-flappers come out and use the wrong term. They're the type that were the C and D losers in junior and senior high.
To David Nelson,
As a matter of fact I am the spelling police and that mistake carries a hefty fine! And yes I'm perfect and make stemakes er I mean mistakes in my typing. This issue is one of the most serious issues of our time so let's treat it with respect. Issues such as the environment and the economy pale in importance by comparison.
P.S. Seriously, let's all lighten up a bit!
One reason Arizona doesn't have DST is that we're at the western edge of the Mountain Time Zone: when we tried it, back in the 1960s, street lights on the California border were coming on at around bedtime. (Also this is after all Arizona, where the supply of sunlight exceeds demand for most of the year.)
And Arizona has a lot of astronomical observatories, where it simplifies things not to have to adjust the clocks twice a year.
I'm not sure what that has to do with anything? Cosmologists mostly work in GMT.
What's the problem with that? I used to live in Louisville, KY, which is in the Eastern time zone although, geographically, it should be on Central time. In the summer, on DST, I could read outside by natural light past 9:30 pm on the longer days. I loved it. I wish we had double DST.
DST should be eliminated it has no use of value in today's modern world.
It was created to give farm workers extra time in the spring and summer.
And there are no farmers and farm workers left in the world? Arrogant white collar prick!
Actually, Joe, farmers tend to dislike DST. Most would rather have the extra hour of daylight in the morning because they often can't take advantage of it in the evening if they have other activities (say, social activities in small communities).
DST is more popular with urban dwellers.
Just split the difference -- 1/2 hour each way & be done with it !!!!!!