The so-called »daylight saving time« (DST) or »summer time«, i. e. setting clocks forward by one hour during the summer months, was introduced in many European countries in the years following the first oil shock in 1973. The objective was to achieve energy savings by better utilizing daylight. In order not to affect the European Single Market, the dates for beginning and ending the DST period have been harmonized within the European Community. The present Directive 2000/84/EC on summer-time arrangements stipulates the application of DST arrangements as mandatory for all EU Member States for an unspecified period.

Since its introduction, there are opposing positions with regard to the benefits of DST in relation to possible negative implications, and a reform of the DST arrangements is called for from different sources. In 2007 for the last time, the European Commission concluded that – apart from the fact that it provides greater opportunities for a wide range of evening leisure activities and produces some energy savings – DST has little impact.

However, the framework conditions under which the implications of DST have to be considered possibly have changed since 2007. Under this impression, the scientific findings and experience regarding DST existing so far have been examined and presented in a general overview for TAB's working report no. 165 »Assessment of daylight saving time«. The central question of the investigation was whether it is appropriate to make a substantial reassessment of the implications of DST compared to the evaluation the European Commission made in 2007.

Results

Implications of daylight saving time for energy consumption

With regard to energy consumption, recent studies also confirm that – at best – only marginal energy savings can be realized. Relating the results of all studies published so far to the national power consumption of the respective countries yields values ranging from -0.9 to 1 % with regard to the impact on power consumption. In the field of room heating, for the most part only marginal effects ranging from -0.2 to 0.2 % are assumed. For air conditioning, the margin ranges between -0.2 and 9 %.

For this, however, only few scientific studies are available so far. Moreover, the studies have been conducted in different countries. As the implications for energy consumption as to their severity and degree strongly depend on the geographic, economic and cultural framework, results obtained in other countries cannot be simply transferred to Germany.

In addition, a survey among almost 700 companies and associations from the German energy industry has been conducted on behalf of TAB in order to gather the experience related to DST gained in this sector. This survey as well did not reveal any indication of DST having a substantial impact on energy consumption.

After all, in model simulations regarding the power consumption of German households for lighting, a reduction in power consumption of less than 0.8 % in relation to the annual power consumption was determined (this corresponds to a decrease of 0.2 % for the national power consumption).

Implications of daylight saving time for the economy

In literature, there is virtually no reliable information or quantitative data with regard to the implications of DST for the economic system. To a very large extent, the few available sources are based on subjective assessments and experience. Based on this, changing the clock in March and October might induce a short-term need for adaptation in individual sectors (i. a. in agriculture or rail traffic). However, this apparently has become a rather unproblematic routine task.

Due to the lacking sources, TAB contacted more than 140 German industry associations, trade unions and professional associations asking them for their opinion on DST. The response rate of this survey was very low. Though the door is left wide open for speculation with regard to the reasons for such a low response, it may be assumed that in case of major difficulties due to the application of DST arrangements in individual sectors there would have been stronger activities by stakeholders from these sectors.

Thus, the insufficient evidence base does not allow for any reliable assessment with regard to the macroeconomic effects of DST – neither in a positive sense e. g. for leisure industry, nor in a negative sense e. g. for the transport sector.

Implications of daylight saving time for health

With regard to possible implications for human health, it is known for a longer period of time already that changing the clock can destabilize humans' system of biological rhythms. In 2007, the European Commission still assumed that »most of the difficulties experienced are of short duration and are not a health hazard«.

Meanwhile, there are more and more scientific indications that the biological rhythms cannot adapt that easily particularly to the clock change in spring. In this context, new findings indicate that even within four weeks after changing the clock, the process of adaptation itself takes place only insufficiently or not at all. In contrast, the clock change in autumn seems to be less problematic.

However, it is unclear which relevant health-related implications result from the disturbances in the biological rhythms caused by the clock change. Due to the partly inconsistent results of the studies, it is not possible yet to make any unambiguous statements in this context. This applies, for example, to possible implications of summer time with regard to the risk of heart attacks, to mental performance or road safety. Further research is required in order to examine the impact of DST on human health in the short and long term in a more detailed way.

Legal situation

A modification of the currently applicable provisions will only be possible by amending the Directive 2000/84/EC on summer-time arrangements within the framework of an ordinary legislative procedure at EU level. Such a procedure could be initiated in four different ways:

• Initiative launched by the European Commission: This case is rather unlikely, as the DST arrangements have been completely harmonized and laid down in perpetuity in the course of the approximation of laws. Moreover, currently no new scientific findings are available which might induce the European Commission to launch an initiative.
• Initiative launched by the European Parliament: Due to its indirect right of initiative, the European Parliament may invite the European Commission to initiate a corresponding legislative procedure. For this, a simple majority in the European Parliament is required. The European Commission is not obliged to meet this request. It also can deliver an unfavourable opinion on such initiatives due to its monopoly of initiative.
• Initiative launched by the European Council: The European Council may also invite the European Commission to take action. For this, a simple majority of the members of the Council is required. In this case as well, the European Commission would not be obliged to initiate a legislative act.
• European Citizens' Initiative: Finally, the citizens of the European Union are also entitled to the right of initiative. A successful citizens' initiative has to be backed by at least 1 million citizens from different EU Member States. But even if this quorum is reached, the European Commission would only be obliged to present its legal and political conclusions on the initiative, the actions it intends to take, if any, and its reasons for taking that action or not.

Conclusion

As a result, the report illustrates that the question whether DST shall be maintained or abolished finally must be subject of corresponding political and societal debates and can fall back on scientific facts only to a very limited extent. Whatever the results of such debates would be: A modification of the currently applicable provisions will only be possible by revising the relevant EU directive within the framework of an ordinary legislative procedure at EU level. The European Commission has discretion whether or not to initiate a corresponding legislative procedure aiming at amending the present provisions.