1Hi, it's Danny.
2Have you heard of daylight saving time?
3You might know it has something to do with clocks.
4In the United States, there's a night in the spring when many people change their clocks.
5They reset the time to go forward 1 hour.
6That's the start of daylight saving time.
7Then, in the fall, people change their clocks to go back 1 hour.
8That's the end of daylight saving time for the year.
9Here, someone named Julio is curious about all this clock changing.
10Let's give Julio a call now.
11Hi, Danny.
12Hi, Julio.
13I have a question for you.
14Why do we have daylight saving time?
15That's a great question.
16Let's start with that first word: daylight.
17Now, you already know some things about daylight.
18Like how we get light from the sun.
19We see the sun in the daytime.
20Then it sets, and it's dark out.
21There's a pattern of daylight and darkness that repeats.
22If you live somewhere with the seasons: winter, spring, summer, and fall.
23You might know about another daylight pattern.
24Let me show you what I mean.
25Here's what the sky looks like when I have dinner in the winter.
26And this is what it looks like when I have dinner in the summer.
27Now, I eat dinner around the same time every day.
28But you can probably spot some differences in these pictures.
29What do you notice about the sky in the winter compared to the summer?
30Maybe you notice that it's darker outside in the winter.
31The sun has already set when I eat dinner.
32But in the summer, it's still light.
33The sun hasn't set yet.
34That's because, in some places, the amount of daylight changes with the seasons.
35There's more daylight in the spring and summer and less in the fall and winter.
36It's a pattern that repeats each year.
37Now imagine you live someplace where the amount of daylight changes with the seasons.
38In summer, for instance, there's sunlight starting early in the morning,
39so early you might still be asleep.
40In the past, that got some people thinking.
41They thought if everyone got up a little earlier,
42they could make use of that morning sunlight.
43And if we did our other activities a little earlier like earlier lunch and earlier dinner,
44we could fit in our evening activities before the sun sets too.
45Now, daylight after dinner might sound great.
46But imagine if you had to go around and convince everyone in your town to wake up early.
47That sounds nearly impossible.
48After all, everyone's got their own schedule.
49But amazingly, that's what daylight saving time is.
50When people set their clocks forward for spring daylight saving time,
51it's like everyone is agreeing to wake up 1 hour earlier.
52Rather than change each person's schedule,
53people in the past realized we could all change our clocks instead.
54And governments passed laws so that all the clocks in a place would change.
55That way, schools start earlier, businesses open earlier,
56buses arrive earlier, and so on.
57By changing the clocks, people can match their daily activities to when there's sunlight in spring and summer.
58And with that sunlight, we need fewer lights,
59so we can use less electricity too.
60But maybe you're curious why we change clocks again in the fall.
61Since fall and winter have less daylight,
62there isn't lots of early morning sunshine to wake up early for.
63So, we change our clocks back for those seasons.
64At least, that's the idea behind daylight saving time.
65But here's the thing:
66the amount of sunlight changes slowly over the seasons.
67Changing our clocks by an hour doesn't always match up.
68It might still be dark when you wake up in spring
69or way too bright when you go to bed in summer.
70And with devices like air conditioners running longer on sunny summer evenings,
71research shows we may use more energy during daylight saving time instead of less.
72Changing clocks isn't helpful for everyone's schedule.
73Some people are up with the sun in every season,
74while others work at night.
75And changing clocks isn't helpful in every place.
76In some places, daylight doesn't change much over the year.
77In fact, for a variety of reasons,
78many places around the world don't do daylight saving time.
79Some have passed laws to get rid of it,
80including the state governments of Hawaii and Arizona.
81Whenever we change our clocks in the spring,
82I feel so tired the next day.
83Maybe you do too.
84That's because if you wake up at your usual time,
85you're actually getting an hour less sleep that night.
86And in the fall, when we change our clocks back,
87it's like we get to sleep in an extra hour.
88That, I don't mind so much.
89But doctors point out that changing our clocks twice a year throws off our sleep schedule.
90It's confusing for our bodies.
91That can lead to worse health and more accidents.
92It's hard to focus when you're tired.
93That's one reason laws have been proposed that could change daylight saving time in the United States.
94We might even stop doing it.
95So, in summary: daylight saving time was invented to help us match our daily activities
96to when there's sunlight in different seasons.
97By changing our clocks 1 hour forward,
98we start our days earlier in spring and summer
99so there will be sunlight for our evening activities too.
100Still, people debate how well that actually works.
101It's helpful to remember that daylight and darkness follow their own patterns that we can't change.
102Changing clocks doesn't change the sun or make daylight.
103It just changes when people are awake to experience that light.
104That's all for this week's question.
105Thanks, Julio, for asking it.