Use Daylight Saving Time As Your Semi-Annual Home Maintenance Reminder

How does DST work?

Around the globe, people set clocks one hour forward on the last Sunday of March. Nevertheless, in the United States, DST starts on the second Sunday of March. Also, the time when the shift occurs differs from country to country. Some regions forward the clocks in the middle of the night at 01:00 am or 02:00 am local time. This practice signifies the arrival of the spring and lasts till the Autumn. Meanwhile, the return to the standard time takes place in October or November.

Keep in mind the process of changing time and recall it easily!

Mnemonics are short but memorable phrases that help to memorize better certain things1.

In the case of the Daylight Saving Time, English speaking people usually use a catchy mnemonic “spring forward, fall back.” It makes sense since the verb spring refers to the forwarding movement and the verb fall implies right the opposite which is a backward movement2.

Check your gutters

You know when you don’t want to have to clean your gutters? In the dead of winter. Hop up on a ladder this weekend and check out your current gutter situation (or make an appointment for someone else to do so). Cleaning out all the dead leaves and debris is going to be much easier now than it will be a month from now, and could save you a costly roof repair bill later. Save yourself the hassle by planning ahead.

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Fall Back in Fall

In the fall (autumn), the DST period usually ends, and our clocks are set back to standard time again. In terms of hours on the clock, we gain one hour, so the day of the transition is 25 hours long.

In effect, one hour is repeated as local time jumps from DST back to standard time. Let’s say that clocks fall back from 2 to 1 o’clock. This means that the hour between 1 and 2 o’clock happens twice during the night of the switch.

It also means that a time like 01:30 (1:30 am) refers to two different moments, which are one hour apart. So if you’re out to meet somebody during that hour—which really lasts two hours—make sure to specify if the meeting is before the switch (first hour) or after it (second hour).

Does DST make sense?

Reverse your ceiling fans

Ceiling fans can spin in two different directions. In the summer, you want the fan’s blade to spin counter-clockwise, which pushes air down. In the winter, it’s better for your fan to spin clockwise, which will pull the cold air up.

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Daylight Saving Time is a great time for you to take a few minutes to dust those fan blades and, while you’re cleaning, to flip the switch on the side to reverse the blades.

System Time

You also need to keep your OS, database and application tzdata files in sync, both with each other, and with the rest of the world, and test extensively when you upgrade. It’s not unheard of that a third party app that you depend on did not handle a TZ change correctly.

Make sure hardware clocks are set to UTC, and if you’re running servers around the world, make sure their OSes are configured to use UTC as well. This becomes apparent when you need to copy hourly rotated apache log files from servers in multiple timezones. Sorting them by filename only works if all files are named with the same timezone. It also means that you don’t have to do date math in your head when you ssh from one box to another and need to compare timestamps.

Also, run ntpd on all boxes.

Spring Forward in Spring

When DST starts in the spring, our clocks are set forward by a certain amount of time, usually by one hour. This means that one hour is skipped, and on the clock, the day of the DST transition has only 23 hours.

Since DST switches usually occur at night to avoid disrupting public life, they snatch away an hour of our usual sleeping time, forcing us to adjust our body clocks. If you set your alarm to the same time as before the clock change, you will sleep an hour less. The good news is that if you work a night shift, you will get away with working one hour less that night.

Spring forward, fall back

Trivia

Finally, governments will sometimes do very weird things:

Standard time in the Netherlands was exactly 19 minutes and 32.13 seconds ahead of UTC by law from 1909-05-01 through 1937-06-30. This time zone cannot be represented exactly using the HH:MM format.

Ok, I think I’m done.

Regulatory institutions

Organizations steering time policy and standards around the world

The system of worldwide time zones was developed by Sanford Fleming back in 1878 but it is still used nowadays. His idea consisted in dividing the world into 24 time zones, giving each part 15º space. The concept came from the fact that the Earth is round and its rotation lasts approximately 24 hours. So this way, the whole surface of the planet would be divided into 24 “slices” each, or 15º because it is what we get if we divide 360 by 24.

However, later it was discovered that Earth’s speed of rotation is slowly going down so there had to be made some adjustments. This is how almost 100 years later, in 1964, was developed a new time scale (UTC) or coordinated universal time. The Daylight Saving Time isn’t taken into account and doesn’t affect it in any way since this new measuring system is completely based on the speed of the Earth’s rotation and its position. The start point is considered to be Greenwich meridian23.

This coordinated time scale is maintained by the Bureau International des Poids et Mesures (BIPM). The BIPM is an international organization established by the Metre Convention, through which all the Standards related to the time measuring are discussed and implemented on the worldwide level24.

The International Earth Rotation and Reference Systems Service (IERS) is the institution responsible for maintaining global time and reference frame standards, notably through its Earth Orientation Parameter (EOP) and International Celestial Reference System (ICRS) groups25.

Nowadays “Official Time” or “legal time” is that prescribed by the law or decree of a sovereign national authority within its own jurisdictional boundaries, which means that every government has a capacity to establish their official time according to the laws that are in force26.

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