Tag Archives: measurement

About daylight saving time

Daylight saving time is a common practice in large swaths of the Western world. I’ve heard many misunderstandings about it, so I thought I’d try to set some straight.


In North America, we call this concept daylight saving time, often rendered as daylight savings time. In most other English-speaking countries, this is called summer time.

As indicated by the non-North American name, DST refers specifically to the summer portion of the year; the winter portion of the year is merely standard time.

What’s the point of DST?

Originally, daylight saving time/summer time was devised to give us more sunlight on summer evenings.

Most of the purposes of DST are obsolete now, so many advocate for getting rid of it altogether.

Am I using EST?

If it’s summer, and you live on the East Coast of the US, you are not using EST. EST stands for “Eastern Standard Time,” which is a term specifically to distinguish it from its summertime equivalent: “Eastern Daylight Time” (EDT). So it is incorrect to say something like “11am EST on August 14th”… unless you actually mean noon in New York time on that day. If you want a term that you can use safely year-round, just use “Eastern Time” (ET).

The nomenclature is equivalent in the other US time zones: Los Angeles’ PST (Pacific Standard Time) switches to PDT in the summer, just as Denver’s MST does to MDT, and Chicago’s CST to CDT. And the terms PT, MT, and CT are acceptable regardless of daylight saving time status.

In Britain, people make the similar mistake of saying GMT (Greenwich Mean Time, their equivalent of EST) year-round. During summer, Britain does not use GMT at all; they use British Summer Time (BST).

To hit the point home, here are the current times in four different timezones (might not work on mobile devices):

Eastern Standard Time
Eastern Daylight Time
Greenwich Mean Time
British Summer Time


DST observance map of the world
Blue: observes DST. Orange: formerly observed DST. Red: never observed DST.
Source: http://upload.wikimedia.org/wikipedia/commons/2/29/DaylightSaving-World-Subdivisions.png

Some countries use DST/summer time, and others don’t. Some have regions that do and regions that don’t (N.B. Arizona and Hawaii, 3 states in Australia, etc.). Some countries or regions used to use daylight saving time but no longer do. Others have changed the dates or times of switching the clocks.

One particularly confusing element is when coordinating between the northern hemispheres. So around March, when DST-observing countries set their clocks forward for summer time, DST-observing countries in the southern hemisphere are turning their clocks backward as their summer time is ending.

Example: São Paulo, Brazil uses GMT -3 hours as its standard time zone. New York City uses GMT -5 hours as its standard time zone. March through October is summer time in the northern hemisphere and winter in the southern hemisphere, so NYC uses Eastern Daylight Time, which is GMT -4 hours (while São Paulo is on standard time: GMT -3 hours). So NYC is 1 hour behind São Paulo. But November through February is winter in NYC and summer in São Paulo – so NYC is in Eastern Standard Time (GMT-5) while São Paulo is in daylight time (GMT-2), making them 3 hours apart.

What’s it look like during the overlap periods between the clock changes? A mess.

Things that DST doesn’t do

You may have grievances about daylight saving time, but there are some things that you just can’t blame on it, like recent droughts or your crops dying.

Let’s share what we learned about the magic of daylight savings time!

In defense of Fahrenheit

I am an American, and I am a firm believer in the metric system. I think it is inherently superior and more logical, plus all but 3 countries in the world have officially adopted it. Having lived abroad, I have been surrounded by meters and liters and kilograms. But there’s one dimension of it that I just can’t agree with.


I forced myself to become fluent in Celsius by switching my weather app and websites over. And like anything else, if you immerse yourself in it, you too can make it second nature. A climate-controlled room began to feel more like 22°C than 72°F. That doesn’t prove anything though.

Here are some of the bones I have to pick with centigrade:

Fahrenheit’s 0°–100° is more practical

Zero to one hundred is the most important segment, and should naturally be applied to the most useful range. Celsius fans boast that freezing is set at 0°C and boiling is set at 100°C, and so it’s obviously the best thing ever… and who has time to remember their oddball equivalents of 32°F and 212°F? But here’s the practicality test: how often do you actually discuss (or have to think about) the temperature of water boiling or freezing? Chances are it’s rare, unless you’re a scientist.

On the flipside, how often do you think/talk about the temperature of the air outside? You probably do this very often, perhaps daily. If you live in a temperate zone, like the majority of humans (and the overwhelming majority of people in industrialized nations), you experience a broad range of temperatures. A frigid winter’s night and a scorching summer’s day punch in around -15°C and 37°C, respectively. Translation: 0°F and 100°F. Now try to tell me those are hard numbers to work with.

The other, rather-practical instance of measuring temperature is when you want to see if someone is feverish. A centigrade fever? A clumsy 38°C and up. A Fahrenheit fever? Above the nice, round, 100°F mark.

Fahrenheit’s more granular

Fahrenheit degrees are smaller, which means they are more specific. Each 1 Celsius degree is equal to 1.8 Fahrenheit degrees.

Example how this might affect you: If your thermostat only has whole-degree settings on it, each Fahrenheit degree you adjust it is finer… 80% finer, to be precise. So Fahrenheit will let you get that much more exact about how you want your house to feel.

“Ah-hah,” you might be saying if you’re wrong Celsius-inclined, “but what if mine has half-degree increments?!” …it’s the same thing all over again. Good ole °F are more precise.

Fahrenheit’s a cooler name

Thirdly, “Fahrenheit” has a significantly cooler ring to it than does “Celcius” or “centigrade”. I can’t give an exact ratio, but I’m pretty sure it’s multiple orders of magnitude. I don’t think Ray Bradbury considered the title Celsius 233 seriously, just as Michael Moore would’ve pooh-poohed Celsius 488.3.


The way I see it, Fahrenheit is the victor.

In the end, though, the clearest loser of the contenders: the Rankine scale.

Image source: http://m.cdn.blog.hu/ju/juharizsuzsanna/image/2012-09/an_original_thermometer_invented_by_daniel_gabriel_fahrenheit_to__auction_zkauf.jpg