Solar Time vs Time Zones: Europe’s Clock Mismatch

I’m always surprised by the fact that most countries in the EU use the same time zone despite their wide variation in longitude.

In many places in Europe the local time does not align closely with the natural time defined by the rising and setting of the Sun. This is particularly true the further west you go. In this article I will explore this discrepancy. But first it is worth clarifying a few terms.

Different Types of time

• The time measured by a sundial is the apparent solar time, sometimes just called the solar time. In solar time the point when the Sun is at its highest in the sky, known as the solar noon, always occurs at 12-noon. Before the widespread use of clocks and watches humans used solar time.
• With solar time, the length of the day varies in a predictable way over the course of the year. It is at its shortest, around 23 hrs 59 mins 40 sec, in mid-September and at its longest, 24 hours 30 secs in late-December. This variation is called the equation of time.

The difference in seconds between the length of a solar day and 24 hours on a given date.

• Mean solar time, assumes that each day is exactly 24 hours long. With mean solar time the solar noon varies between 11:44 AM and 12:14 PM during the year, but its mean value is 12-noon.
• After accurate clocks became widely available, but before the advent of the railways, mean solar time replaced apparent solar time as the civil time for day to day timekeeping.
• Mean solar time is 4 minutes later for each degree in longitude eastward. Rather than each place having its own local civil time (based on its local mean solar time), which would cause massive confusion, and make timetables near impossible to construct, the world is divided into time zones.
• Time zones are normally a whole number of hours ahead of or behind UTC (Coordinated Universal Time).
• UTC is the standard time measured by accurate atomic clocks and is based upon GMT, Greenwich Mean Time, which is the mean solar time on the line of zero longitude. The terms UTC and GMT are often used interchangeably but UTC should be used in precise writing.

What is natural time

Natural time is the time which aligns locally to the rising and setting of the Sun.

If we take a location, on the zero longitude line, which uses the UTC time zone, the local time will be the same as the mean solar time. UTC can be considered the natural time, for this location. On average the Sun would be at its highest in the sky at 12-noon and there would be an equal number of hours of daylight in the morning and in the evening

For every 15 degrees of longitude we move east, the natural time is one hour ahead of UTC and for every 15 degrees of longitude we move west, the natural time is one hour behind UTC.

Natural Time Zones

The countries in Europe (except Russia and to a much lesser degree Norway) span a small range of longitude. Therefore, I have allocated each European country (except Russia) to a single natural time zone, a whole number of hours ahead or behind UTC, based on the longitude of the capital city rounded off to the nearest 15 degrees.

In these natural time zones, average solar noon occurs between 11:30 AM and 12:30 PM at the country’s capital. With the exception of Norway, most if not all of the rest of the country also has an average solar noon between 11:30 AM and 12:30 PM.

The map of the natural time zones of Europe is as a follows.

Turkey, Russia, and the countries in the Caucasus excluded.

(*) The longitude of Ajaccio the capital of Corsica, is 8.73 ^oE. If Corsica were an independent country, instead of being part of France, its natural time zone would be UTC +1.

(**)The longitude of Bern, the capital of Switzerland is 7.448^oE which (only just) puts Switzerland into the UTC natural time zone, but Bern is only the fifth most populous city in Switzerland. If the allocation had been based on its most populous city Zurich (longitude 8.54^oE) then Switzerland would be in UTC +1.

Comparison of Natural Time Zone with Local Time

The only European countries which have a single time zone and do not advance their clocks one hour in March and put them back by one hour in October are Iceland and Belarus.

If we compare the natural time zone to the local time, then between October and March.

• Iceland, Portugal, Spain, France, Belgium, Holland, Luxembourg, Switzerland and Belarus are one hour ahead of their natural time zone.
• All other countries are on their natural time zone.

If we compare the natural time zone to local  time between March and October.

• Portugal, Spain, France, Belgium, Holland, Luxembourg and Switzerland are two hours ahead of their natural time zone.
• All other countries are one hour ahead of their natural time zone.

Local Time in Spain

Spain has the worst fit of any country in Europe between its civil time and local solar time.

Most of the EU is on the same time zone (UTC+1 or UTC+2 during DST). There are a number of reasons for this. It makes timetabling and planning journeys easier if there are no time zone changes to consider. It avoids confusion when scheduling calls and meetings across European states. Cross border working and meeting up for social events are easier to plan if everyone uses the same time zone.

As we’ve seen, the local time is a good fit to the natural time in central Europe in the winter months and is about one hour ahead of the natural time during DST. For example:

• In Warsaw (long 21.01 ^oE) the average solar noon occurs at 11:36 AM or 12:36 PM (during DST).
• In Vienna (long 16.37 ^oE) it occurs at 11:55 AM or 12:55 PM (during DST)
• In Berlin (long 13.41 ^oE) it occurs at 12:06 PM or 1:06 PM (during DST)

As you go further west in Europe, the more out of step local time becomes with the natural time.In Madrid the average solar noon occurs at 1:15 PM or 2:15 PM (during DST). In Vigo in northeast Spain (long 8.71 ^oW) average solar noon occurs at 1:35 PM or 2:35 PM (during DST).

The extreme mismatch between solar time and local time in Vigo means that even on the date of the June solstice, when the hours of daylight are at their greatest, the Sun still doesn’t rise until 6:58 AM. But it doesn’t set until 10:14 PM, nearly one hour later than in London, which is 9.28^o of latitude (or 1030 km) further north. During the winter months, when the hours of daylight are at their shortest, the Sun never sets any earlier than 6 PM in Vigo. On the day of the December solstice, it doesn’t rise until 9:00 AM and sets at 6:05 PM.

Interestingly, Spain used to be on UTC or UTC+1 during DST, the same as the UK. In 1940 under General Franco, it switched its local time to be the same as central Europe and never switched it back. The lighter evenings have become part of Spanish culture.

People in Spain tend to eat and go out in the evening later than the other nations in Europe. It is likely that the later sunsets give a boost to hospitality, outdoor dining, and evening tourism revenue. Although opinion is split on the issue there doesn’t appear to be a strong movement to return civil time back to align more closely to mean solar time.

France also used to be on UTC or UTC+1 during DST. In 1940 after the German invasion during the Second World War, it switched its local time to be the same as central Europe. It never switched back at the end of the war.

Local Time in Norway

Norway spans a greater range of longitude than any country in Europe, other than Russia. Its westernmost town Florø lies at a longitude of 5.03 ^oE . On average solar noon there is at 12:40 PM (1:40 PM during DST). If individual regions of a country had their own times zones, the natural time zone of Florø would be UTC, the same as London. The second and fourth largest cities in Norway: Bergen and Stavanger would also have UTC too

Norway’s easternmost town Vardø lies at a longitude of 31.11 ^oE, further east than St Petersburg, Kiev and Istanbul. Its natural time zone is UTC +2, but it uses UTC+1 or UTC+2 (during DST) like the rest of Norway . In Vardø during the winter months the average solar noon occurs at 10:56 AM local time.

It lies at a latitude of 70.37 ^oN , well above the Arctic Circle. At this latitude, the Sun is below the horizon for nearly 2 months from November 24 until January 18. The unusual offset of the local time from the solar time in winter means that for two short periods before and after the Sun disappears for the winter it sets before noon!

Should we move back to natural time?

In the UK, like many countries which use Daylight Saving Time, there is often a debate about whether to abolish these twice yearly clock changes and if so, should the UK use UTC all year round, its natural time zone? Or should itvuse UTC+1?

From 1968 until 1971 the UK kept its clocks at UTC+1 all year round. However, the trial proved unpopular in Northern England, Northern Ireland and Scotland because of the ensuing darker mornings at higher latitudes and westerly longitudes. In Edinburgh, the Sun didn’t rise until 9:42 AM on the date of the winter solstice and in Steòrnabhagh (Stornaway) in Leòdhas (the Isle of Lewis) in far northwest of Scotland it didn’t rise until 10:12 AM.

Because of this opposition from the north and west of the UK and a more general wider dislike of the darker mornings, in December 1970 the UK’s House of Commons voted 366 to 81 against continuing the trial.

Some organisations such as the British Sleep Society have proposed we should return back to a civil time which aligns with the rising and setting of the Sun and that this would be beneficial for human health. I agree with them!

There is an ongoing debate in the United Kingdom and in other countries about whether twice-yearly changes into and out of Daylight Saving Time should be abolished. Opinions are divided about whether any abolition of Daylight Saving Time should result in permanent Standard Time, or year-long Daylight Saving Time. The British Sleep Society concludes from the available scientific evidence that circadian and sleep health are affected negatively by enforced changes of clock time (especially in a forward direction) and positively by the availability of natural daylight during the morning. Thus, our recommendation is that the United Kingdom should abolish the twice-yearly clock change and reinstate Standard Time [GMT] throughout the year. [1]

Further Notes on UTC

From 1972 until 2026 UTC, the international time standard determined by atomic clocks, used to be tied to the time standard determined by the Earth’s rotation Universal time (UT1) (which in practical terms is the same as GMT) by periodically adding leap seconds. The aim being to keep the magnitude of the difference between UT1 and UTC to be less than 0.9 seconds. Effectively this locked UTC to the natural time (or mean solar time) on the zero longitude line. Currently UT1 is 0.1 seconds ahead of UTC.[2].

However, leap seconds are troublesome to implement. Following a resolution by the General Conference on Weights and Measures (CGPM), in October 2026, the maximum difference between UTC and UT1 has been increased to one hour [3]. So, in future UTC will not be tightly locked to the mean solar time on the zero longitude line.

As the Earth’s rotation slows, over the centuries UTC will drift ahead of UT1(and thus GMT) until an entire leap hour is needed to bring it back in line. However, no one reading this post will be around to experience the leap hour, it will take thousands of years before this happens 🙂 and I sure that there will be many more changes to how UTC is defined before we get to that point!

And Finally….

If you’d like to find out more about the difference between local and mean solar time, you may be interested in this Explaining Science video.

References

[1] Crawford, M.R., Winnebeck, E.C., Schantz, M. von, Gardani, M., Miller, M.A., Revell, V., Hare, A., Horton, C.L., Durrant, S. and Steier, J. (2024). The British sleep society position Statement on Daylight saving time in the UK. Journal of Sleep Research. [online] doi:10.1111/jsr.14352. (Accessed 25 Oct 2026)

[2] NIST. (2009). Leap second and UT1-UTC information | NIST. [online] Available at: https://www.nist.gov/pml/time-and-frequency-division/time-realization/leap-seconds [Accessed 26 Oct. 2026].

[3] BIPM. (2026). Resolution 5 (2026) – BIPM. [online] Available at: https://www.bipm.org/en/cgpm-2026/resolution-5 [Accessed 26 Oct. 2026].