Summer time and Daylight Saving time (DST)

However, there is one slightly change in time we all do accept. That is the concept of "summer time" (Daylight saving time, DST), one hour which is stripped or added. The concept of summer time is about one hundred years old and became popular in Europe in the beginning of the 1970ies. It was the time of energy crisis, the Oil Crisis of 1972. 1975 several European countries decided to install a Summer time. However, does this one hour really save daylight and therefore energy?

The concept of a summer time, however, only makes sense in the middle latitudes of the earth, since at the equator there is nearly no fluctuation of day time. The day has always the same length here and the sun rises exactly at the same time. Only in the north and south the length of day differs, up to the mid-summer night in the polar region. But, does this one saved hour in really compensate the energy output of the sun?

Now we have to focus on the basic philosophy which made the people to create a summer time. The first time a summer time was installed was during the WW I, in 1916, to save energy, which was needed for the war industry. A summer time was also used during WW II and then again in 1975, after the shock of the oil crisis of 1972. The basic thought was to save energy by effectively using the day light. However, this focus is only sound, when you focus either on the morning or the evening. The day does not get longer or shorter by introducing a summer time. The time between sunrise and sunset is still the same. What changes is the local time, which is often politically installed. A later sunset therefore means also a later sunrise. This makes energy saving complicated, because the effect of saving is only apparent when we focus on night or day. Most politicians focused on the evening. After work people like to stay together, have dinner and recreate. It was thought that due to a summer time people stay outside, doing outside activities and do not turn on the lights so early. However, this may have been true for the 1970ies.

Today, our everyday lives have changed. The daily habits focus today more on inside activities. Even if the sun is rising, most people stay inside. Since also working hours changed, many people do not even have free time so early, but come home very late from work. Saving electricity is not possible in those cases. As I have mentioned already, a later sunset means also a later sunrise. If we also consider about morning activities, the energy saving decreases enormously, because people have to turn on lights in the morning. Today more people have to wake up earlier and go to work earlier, even school children have often a longer way to school, so they will wake up early. Since 1970 a shift in daily behaviour went through society and this lead to a discussion, if summer time is needed at all. It is true that a summer time could save some energy, but in reality it does not, because human activity hours are not congruent with the summer time. Further, more and more people complain about the time changes, feeling dizzy and tired. The costs of ineffective working during the days of time change in March and October are often considered as higher than the amount of saved energy.

We have seen that the concept of time zones is a sound and effective system of matching local time to real time. The summer time concept (Daylight saving time, DST) does not save energy at all, since daily activities are too individual and our recent society focuses more on inside activities than on outside activities. It does in many cases not matter if there is still daylight or not - we have accommodated to an environment which uses energy. The amount of electricity saved by not turning on the lights is small compared to it of all other energy using machines we use now (computers, TV, mobile phones, ...). The summer time concept is more a tradition than an effective instalment.