Millions of people will have a glass of bubbly ready to welcome the new year on Monday night, but how will they know when to quaff it? Who is in charge of telling us what time it is and when we should hear the stroke of midnight?
Citizens of the Republic have to go abroad to get this service. We don't have a government department or civil servants to make sure that clocks across the State remain in accord. Instead we rely on satellites, time signals from Rugby, in England, and, to a growing degree, on the Internet.
Most people just switch on the radio or television to set their watches or dial up the speaking clock. Different parts of RT╔ get their time from different sources: the radio stations get it from Rugby, the television stations from Global Positioning System satellites and the web service from the Internet.
We rely on others for this important service mainly because it is expensive to maintain the primary time source of an atomic clock. Britain, the United States, France and many other countries do have atomic clocks and, following international agreements, pool the clocks' time to arrive at an agreed average, called Co-ordinated Universal Time (which has superseded Greenwich Mean Time). This is overseen by an international body based in France, the Bureau International des Poids et Mesures.
The state of the art in timekeeping, caesium atomic clocks provide the backbone of world time. Microwaves are used to make atoms of caesium 133 vibrate at one of their fundamental frequencies, 9,192,631,770 cycles per second. This splits a second down into billionths of a part and allows an accuracy of two billionths of a second per day, or one second in about 1.4 million years.
With one of these clocks in your living room you would know for sure when midnight arrived, but there wouldn't be much room for anything else, given their size. Yet this level of accuracy is still not good enough for Co-ordinated Universal Time. There is no one single atomic clock minding the time for us: there are large collections of them.
The US has a master clock at its Naval Observatory, in Washington DC, but it constantly compares and adjusts its time against an ensemble of 70 other caesium clocks in 18 secure vaults. And this master clock is only one of a number of similar ensembles of atomic clocks whose times are pooled at the bureau, outside Paris, to create Co-ordinated Universal Time.
All of this is a far cry from the way Ireland used to get its time, which until 1916 was different from that in Britain. Dublin was 25 minutes and 22 seconds behind London, given its more westerly location.
From the 1780s and well into the last century, the Dunsink Observatory, founded by Trinity College in 1783, set Ireland's time. The observatory's first regular time observation using the movements of the stars was taken in August 1785 by Henry Ussher, using a four-foot transit instrument. Once set, the operator watched until a given star reached the transit cross hairs, linking that moment with a given moment of solar time.
Dunsink commissioned a pair of long-case regulator clocks from John Arnold, a noted London clock-maker, to help keep Ireland's time, and the two still sit in the observatory's library. "They are quite famous," says Dr Ian Elliott, formerly of Dunsink. "John Arnold and his son were amongst the pioneers of clock-making. They are the pride and joy of the place."
One clock was set to maintain sidereal, or star, time - our own master clock - and the second to Dublin, or solar, time. The sun is quite inaccurate when it comes to timekeeping and can sometimes create an error of up to 15 minutes, because of a calculation known as the equation of time.
The Dunsink measurements were wired to the former ballast office, at the corner of Westmoreland Street and Aston Quay, in Dublin, which made the time available to ships' captains so they could set their chronometers for accurate navigation.
Dunsink and the Dublin Port and Docks Board introduced a piece of new technology in 1865 to make this easier: a "time ball" on the roof of Custom House that descended to mark 1 p.m. Dublin time (13:25:22 GMT). The captains could rest easy on their tall ships and set their time by watching the ball.
An act of the UK parliament set a single time for Britain and Ireland, but the ball - and so Dubliners - continued to keep local time behind London's. In 1914, the ball was finally adjusted to Greenwich Mean Time, but many locals persisted with Dublin time until the ball was removed to the hailing station at Sir John Rogerson's Quay. On October 1st, 1916, Ireland finally adopted GMT.
Although Dublin time is no more, you could argue that its vestiges remain. Just watch the clock as you await guests due at 9 p.m. for a New Year's Eve bash and see when they actually arrive.