Why do we have daylight savings time and when did it start?

As its name suggests, the purpose daylight savings time (changing the time) is to make better use of daylight and therefore save energy. Benjamin Franklin, one of America's founding fathers, mentions the time change in a letter from 1784 "The Cost of Light." Franklin humorously criticized the consumption of candles and suggested waking people up at sunrise to make better use of sunlight.

Photo: Pixabay.com

For the first time, official daylight saving time was first introduced in Germany in 1916. In addition to saving raw materials, workers in the arms industry should be able to make better use of the days. After the end of the war, the government of the Weimar Republic abolished the time change. In the meantime, countries like France and Great Britain have also imposed daylight saving time on their populations. 

The National Socialists reintroduced daylight saving time to support the war economy from 1940 to 1945. In the postwar years with the division of Germany into occupation zones, things became even more complicated because in the West and the East, different times or summer times applied. The changeover was suspended again in 1950, until the oil crisis of the 1970s.

With a decision by the European Union, since 1996 uniform dates for the time change to summer time have been in effect throughout the European Union:

• On the last Sunday in March, the clock is put forward one hour from 2 am to 3 am
• On the last Sunday in October, the clock is set back from 3 am to 2 am

Effects of summer and winter time

The assumption that the clock change could have a positive effect on energy consumption has not been confirmed. Less electricity for lightning is actually used in the evenings during summer, but on the other side, more heating power is used in the morning in spring and autumn. 

Thus the increased consumption of heating energy compensates for the electricity saved. Also with the introduction of energy-saving lamps, time change has lost its original purpose.

Does daylight Savings affect mental health?

There are many research papers that warn about the massive effects of the time change. The time change affects the body like a little jet lag, from which people with sleep disorders and organic disorders suffer particularly. The reason for this lies in the disruption of the internal biological clock, which is disrupted by the time change. It also causes problems for domestic animals, especially those raised on farms. For example, by changing the working hours of farmers, the biological clock of breeding animals, such as cows, or sheep’s is disturbed, and certain period of adjustment is needed.

Why is a day on earth 24 hours long?

The day lasts 24 hours just because people wanted to share it like this. There is nothing in nature about hours, minutes and seconds. This division of time was made by man according to his wish.
But there is something in nature that happens in one day. Each time the Earth rotates once about its axis, a certain time passes, which we call a day. Using stars, scientists can accurately measure time. In observatories, a day begins when a star crosses the meridian and lasts until it crosses it again.

Since man divided the day into hours, minutes and seconds, we can say exactly how long a day lasts: 23 hours, 56 minutes, and 4.09 seconds. This is called a sidereal day. But since it would be difficult to use sidereal day in practical life, we take the day to last 24 hours, so we add a leap year to correct the difference.

Image by Gerd Altmann from Pixabay

In the old days, people thought that the day lasted from sunrise to sunset. The duration of the night was not counted. The Greeks reckoned that the day lasted from sunset to sunset and the Romans from midnight to midnight.
While the clocks had not yet been discovered, it was calculated that day and night lasted 12 hours each. Such a division was not practical, as the length of day and night varied between seasons. Today in most countries, the law stipulates that the day lasts 24 hours, from midnight to midnight, according to Roman times.

How to Set a Sundial

The sundial is an instrument for measuring time by using the shadow of the sun. They were quite common in ancient times before clocks and watches were invented. At the present time they are used more as an ornamentation than as a means of measuring time, although they are quite accurate if properly constructed.
There are several different designs of sundials, but the most common, and the one we shall describe in this article, is the horizontal dial. It consists of a flat circular table, placed firmly on a solid pedestal and having a triangular plate of metal, Fig. 1, called the gnomon, rising from its center and inclined toward the meridian line of the dial at an angle equal to the latitude of the place where the dial is to be used.
The shadow of the edge of the triangular plate moves around the northern part of the dial from morning to afternoon, and thus supplies a rough measurement of the hour of the day.
The style or gnomon, as it always equals the latitude of the place, can be laid out as follows: Draw a line AB, Fig. 1, 5 in. long and at the one end erect a perpendicular BC, the height of which is taken from table No. 1. It may be necessary to interpolate for a given latitude, as for example, lat. 41 degrees-30'. From table No. 1 lat. 42 degrees is 4.5 in. and for lat. 40 degrees, the next smallest, it is 4.2 in.
Their difference is .3 in. for 2 degrees, and for 1 degrees it would be .15 in. For 30' it would be 1/2 of 1 degrees or .075 in. All added to the lesser or 40 degrees, we have 4.2+.15+.075 in.= 4.42 in. as the height of the line BC for lat. 41 degrees-30'. If you have a table of natural functions, the height of the line BC, or the style, is the base (5 in. in this case) times the tangent of the degree of latitude. Draw the line AD, and the angle BAD is the correct angle for the style for the given latitude. Its thickness, if of metal, may be conveniently from 1/8 to 1/4 in. ; or if of stone, an inch or two, or more, according to the size of the dial. Usually for neatness of appearance the back of the style is hollowed as shown.
The upper edges which cast the shadows must be sharp and straight, and for this size dial (10 in. in diameter) they should be about 7-1/2 in. long.

Details of Dial

TABLE No. 1.
Height of stile in inches for a 5in. base, for various latitudes

To layout the hour circle, draw two parallel lines AB and CD, Fig. 2, which will represent the base in length and thickness. Draw two semi-circles, using the points A and C as centers, with a radius of 5 in. The points of intersection with the lines AB and CD will be the 12 o'clock marks. A line EF drawn through the points A and C, and perpendicular to the base or style, and intersecting the semicircles, gives the 6 o'clock points. The point marked X is to be used as the center of the dial. The intermediate hour and half-hour lines can be plotted by using table No. 2 for given latitudes, placing them to the right or left of the 12-o'clock points. For latitudes not given, interpolate in the same manner as for the height of the style. The 1/4-hour and the 5 and 10-minute divisions may be spaced with the' eye or they may be computed.

Table No. 2.
Chords in inches for a 10 in. circle Sundial.

When placing the dial in position, care must be taken to get it perfectly level and have the style at right angles to the dial face, with its sloping side pointing to the North Pole. An ordinary compass, after allowing for the declination, will enable one to set the dial, or it may be set by placing it as near north and south as one may judge and comparing with a watch set at standard time. The dial time and the watch time should agree after the watch has been corrected for the equation of time from table No. 3, and for the difference between standard and local time, changing the position of the dial until an agreement is reached. Sun time and standard time agree only four times a year, April 16, June 15, Sept. 2 and Dec. 25, and on these dates the dial needs no correction. The corrections for the various days of the month can be taken from Table 3. The + means that the clock is faster, and the means that the dial is faster than the sun. Still another correction must be made which is constant for each given locality. Standard time is the correct time for longitude 750 New York, 900 Chicago, 1050 Denver and 1200 for San Francisco. Ascertain in degrees of longitude how far your dial is east or west of the nearest standard meridian and divide this by 15, reducing the answer to minutes and seconds, which will be the correction in minutes and seconds of time. If the dial is east of the meridian chosen, then the watch is slower; if west, it will be faster. This correction can be added to the values in table No. 3, making each value slower when it is east of the standard meridian and faster when it is west.

The style or gnomon with its base can be made in cement and set on a cement pedestal which has sufficient base placed in the ground to make it solid.

The design of the sundial is left to the ingenuity of the maker.

Table No. 3
Corrections in minutes to change.
Sun time to local mean time,- add those marked + subtract those
Marked - from Sundial lime.

—Contributed by J. E. Mitchell, Sioux City, Iowa.

Excerpt from the book:
THE BOY MECHANIC
VOLUME I
700 THINGS FOR BOYS TO DO
WITH 800 ILLUSTRATIONS
1913, BY H. H. WINDSOR CHICAGO
POPULAR MECHANICS CO. PUBLISHERS

How Many Days in Each Month - Easy Hand Trick

"Thirty days hath September, April, June and November," etc., and many other rhymes and devices are used to aid the memory to decide how many days are in each month of the year. Herewith is illustrated a very simple method to determine the number of days in any month. Place the first finger of your right hand on the first knuckle of your left hand, calling that knuckle January; then drop your finger into the depression between the first and second knuckles, calling this February; then the second knuckle will be March, and so on, until you reach July on the knuckle of the little finger, then begin over again with August on the first knuckle and continue until December is reached. Each month as it falls upon a knuckle will have 31 days and those down between the knuckles 30 days with the exception of February which has only 28 days. —Contributed by Chas. C. Bradley, West Toledo, Ohio.

The Knuckles Designate the 31 Day Months


Excerpt from the book:
THE BOY MECHANIC
VOLUME I
700 THINGS FOR BOYS TO DO
WITH 800 ILLUSTRATIONS
1913, BY H. H. WINDSOR CHICAGO
POPULAR MECHANICS CO. PUBLISHERS

Sidereal Time And Solar Time – Why day lasts 24 hours?

The day lasts 24 hours just because the humans wanted to share it in such manner. 

There is nothing in nature that is related to the hours, minutes and seconds. This change in time the humans made according to their wish.
But there is something in the nature of what is going on in one day. 
Every time when the Earth turns around its axis, we call this period a “day”. Using the stars, scientists can accurately measure the time with Sidereal.
One “Star” day starts when one star passes through one meridian, and lasts until the moment when it passes this meridian again.

As the time is divided in hours, minutes and seconds, we can exactly tell how long lasts one “Star” day: 23 hours , 56 minutes and 4.09 seconds. 

But since it would be difficult to use in practical life the “Star day” we take that the day lasts 24 hours, and we add one day to the leap year (February 29th) to compensate for these differences.
In the old days, people thought that the day lasts from sunrise to sunset.
The duration of the night was not taken in consideration. The old Greek people reckoned that day lasts from one to another sunset, and the Old Romans from midnight to midnight.
Until the construction of the Sidereal, it was considered that both day and night last 12 hours.
Such division was not practical, because the length of day and night differed in certain seasons.
Today in most countries, with law is established that day lasts 24 hours, from midnight to midnight, according to the Old Roman measuring.

Sidereal time vs solar time. Above left: a distant star (the small red circle) and the Sun are at culmination, on the local meridian. Centre: only the distant star is at culmination (a mean sidereal day). Right: a few minutes later the Sun is on the local meridian again. A solar day is complete.