The new millennium

Why is 2000 a leap year? | When will the 3rd millennium start? | Why the Millennium starts at zero hours at Greenwich? | The first sunrise of the new Millennium

NB this page was prepared in 1999 to answer questions about the forthcoming new millennium. Although we are now well into the 3rd millennium, the questions and answers have been left in the future tense.

This page covers the most frequently asked questions regarding the start of the new (Christian, Gregorian) millennium.

Why is the year 2000 a leap year?

Leap years were introduced into the calendar by Julius Caesar to ensure that the months of the year stay in step with the seasons. This is necessary because the Earth makes one rotation of the Sun in 365.24219, which is clearly not a whole number of days. Adding one extra day every four years would exactly correct for a year of length 365.25 days but will over correct for a year of length 365.24219. To make a more exact correction the Gregorian calendar, introduced in 1582, stated that a century year will only be a leap year if it is divisible without remainder by 400, which is the case for the year 2000. This approximation corresponds to an average year length of 365.2425 days and will amount to a discrepancy of only one day after 4000 years. The Gregorian calendar was adopted in Britain in the year 1752 when 2 September was followed by 14 September.

When will the 3rd Millennium and the 21st century start?

A millennium is an interval of 1000 years and a century is an interval of 100 years. In the Gregorian Calendar, which we use, there is no year zero and the sequence of years near the start runs as follows;

..., 3BC, 2BC, 1BC, 1AD, 2AD, ...

Because there is no year zero, the first year of the calendar ends at the end of the year named 1AD. By a similar argument 100 years will only have elapsed at the end of the year 100AD. Since 2000AD is the 2000th year of the Christian calendar, it will be the last year of the 2nd millennium. So the 3rd millennium and the 21st century will begin at the same moment, namely zero hours UTC (commonly known as GMT) on 1 January 2001.

We have received a great deal of e-mail regarding the start of the 21st century. It is interesting to note that this is not the first time that this controversy has arisen. The Times newspaper must have received many letters towards the end of 1799, since its editors felt moved to make the following comments about the beginning of the 19th century:

We have uniformly rejected all letters and declined all discussion upon the question of when the present century ends, as it is one of the most absurd that can engage the public attention, and we are astonished to find it has been the subject of so much dispute, since it appears plain. The present century will not terminate till January 1, 1801, unless it can be made out that 99 are 100... It is a silly, childish discussion, and only exposes the want of brains of those who maintain a contrary opinion to that we have stated
The Times, 26 December 1799

The origin of the Christian era

Early in the 6th century AD, Dionysius Exiguus (Denys the Little), a monk and astronomer from Scythia now south-west Russia, compiled a table of dates for Easter in terms of the Diocletion calendar. He decided to reset the system of counting years to honour the birth of Christ so that the year 248 Anno Diocletiani became the year 532 Anni Domini Nostri Jesu Christi, known as 532 AD for short. In his scheme he believed that Christ was born on 25 December of the year preceding the start of the year 1 AD. There is no year 0 AD preceding the year 1 AD. Indeed, the concept of counting from zero, rather than one, does not exist in Latin and was introduced into Europe from the Middle East many centuries later. Therefore, Dionysius' calendar places the birth of Jesus Christ at the end of the year 1BC. The 2000th anniversary of Christ's birth would then be 25 December 2000. However, modern research indicates that Christ was probably born in 6BC and certainly by 4BC, when Herod died.

The idea of naming years BC was introduced by Bede in the 8th century. Naming years in the Christian Era came into common use in ecclesiastical circles in the Middle Ages but was not adopted for civil use until later.

More information about Dionysius and the medieval calendar can be found at the US Naval Observatory website.

Other calendars and eras in use

Apart from the Christian calendar, there are about 40 other calendars in use throughout the world. A few of them are listed, showing their years on 1 January 2000; Byzantine 7508, Chinese 4636, Indian (Saka) 1921, Islamic (Hegira) 1420, Jewish (A.M.) 5760. The date on which the year changes is different for each calendar.

See our fact file on the calendar

Why the Millennium starts at zero hours at Greenwich

The international conference held at Washington for the purpose of fixing a Prime Meridian and a universal day in October 1884, resolved to adopt the meridian at Greenwich as the prime meridian for 'all the world' and the time and day at the Greenwich meridian, Greenwich Mean Time (GMT) as the basis for the universal day. Today GMT is more correctly referred to as Coordinated Universal Time (UTC). This forms the basis for our claim that the Millennium started at zero hours Greenwich time. The same conference stated that the 'universal day shall not interfere with the use of local or other standard time where desirable.' Put simply this means that in Sydney they are not going to wait until 10 next morning before celebrating the New Year.

Where is the Greenwich Meridian?

The famous brass strip seen at the Royal Observatory, Greenwich, marks the Airy meridian referred to in the 1884 treaty. However the meridian to which the UK Ordnance Survey is tied lies 5.7 9m to the west while the GPS satellite meridian lies 102.51 m to the east. See 'The longitude of Greenwich'

The International Date Line

The international dateline is an imaginary line of longitude located about 180° east (or west) of the Greenwich meridian. This is the line across which the date changes by one day. To understand this imagine it is 15.00 GMT on 3 January at Greenwich. 15° east of Greenwich the local time will be 16.00, one hour ahead. In Japan, 135° east it will be nine hours ahead and the local time will be 00.00 on 4 January, while in E Australia, 150° east it will be 01.00 on 4 January. In New Zealand, close to the International Date Line, the local time is 03.00 on 4 January.

Now let us return to Greenwich and imagine travelling west towards America. For every 15° we travel the local time is an hour behind. For example the local time in California is 07.00 on 3 January. As we continue west towards the International Date Line the local time falls further behind, until at the date line the time is 03.00 on 3 January. This illustrates two things, firstly that there is no change of local time crossing over the date line although the date changes by one day and secondly, the obvious value in adopting a standard time and day that can be used to date events anywhere in the world without ambiguity.

Legal status of the International Date Line and Kiribati

Despite its name, the International Date Line has no international status and was not defined by the 1884 convention or any other treaty. This means that countries close to the Date Line are free to choose which date they will observe.

On 23 December 1994 the Republic of Kiribati announced that:

'with effect from 1 January 1995 all islands in the Line and Phoenix Groups within the Republic of Kiribati shall be on the same date of the islands in the Gilberts Group within the Republic while their time are maintained to what they are as at present'.

This perfectly reasonable decision from an administrative point of view, puts a large eastward bulge in the International Date Line. It also places Caroline Island, since renamed Millennium Island, as a leading contender to see the first sunrise of the millennium.

Fiji and longitude 180°

The Islands of Vanua Levu, Rambi and Taveuni, all part of Fiji, have the distinction of being the only islands crossed by the 180° line of longitude in the Pacific. The other places where the 180° longitude crosses land are, Wrangel Island (Vrangelya Ostrov, 71° north), far NE Russia and Antarctica. The highest peak on the Island of Taveuni, called Uluinggalau or Uli i Ngalu, lies just 200 meters west of the 180 longitude! Although not a leading contender to see the first sunrise this is clearly a place of great geographical interest. The Sun will rise at the point where the 180 longitude crosses the coast of Taveuni, 9 km to the south of Uluinggalau, six minutes after it is seen to rise from the top of Uluinggalau.

The first sunrise of the new Millennium

The purist view

If we accept that the New Millennium only starts at zero hours UTC on 1 January 2001 then the question is simply where is the Sun rising at that instant. The answer is that it is rising along half a great circle running from Eastern Russia, through China out over the Bay of Bengal and down towards the Antarctic circle. On its way across the Bay of Bengal, it crosses Katchall Island, an Island in the Nicobar Group of Islands.

The view From Antarctica

At the South Pole the Sun will have risen at the previous equinox, on 22 September 2000, and will not set until the following equinox, on 20 Mar 2001. Does this make the South Pole the first place to see the first Sunrise of the new Millennium on 22 September 2000 or only the last place to see the last Sunset of the old Millennium?

The US Naval Observatory has pointed out that the Sun will set and then rise in Antarctica, at longitude 135 degrees East on the headland between the Dibble Glacier and Victor Bay, at 15:08 UT on 1 Jan 2000. However, it will only have been below the horizon for less than half an hour that night!

The local time view

It is common cause that the start of the New Year is celebrated by people around the world according to their own local times and that most people will celebrate the start of the year 2000 not 2001.

We have listed the times of sunrise for a number of places at the start of the year 2000 in a table which you can view via the right hand column of this page. In practice the difference in times between 2000 and 2001 is negligible. There are also a series of sunrise maps showing the sunrise over several places stated in the table. Please note the maps are copyright Dr Andrew Sinclair and may not be reproduced without permission.

Will the Sun rise at the time stated?

The calculation of the time of sunrise depends on using a model for the way the Earth's atmosphere bends light. For example when the entire disk is seen to be above the horizon the real Sun is still just below the horizon. An average model of the atmosphere is used so that the actual time of sunrise can vary by at least one minute, depending on actual conditions.

Time and place of first sunrise in the UK on 1 Jan 2000

South Foreland close to Dover, will be the first place in the UK to see the Sun rise on 1 January 2000 at 07.58.

The last sunset and the first sunrise

Anyone that accepts that the first sunrise of the New Millennium will be seen from Caroline Island has the possibility of flying 1500 miles west to Samoa and seeing the last sunset of the old Millennium, 14 hours and 14 minutes later.