The first thing most people do when visiting the Royal Observatory, home of Greenwich Mean Time, is to straddle the Meridian Line where east meets west. Charles II founded the Observatory in 1675 and appointed John Flamsteed as his first Astronomer Royal “to apply himself to the rectifying the tables of the motions of the heavens, and the places of the fixed stars, so as to find out the so- much-desired longitude of places for the perfecting the art of navigation”. You can wander around the time and space galleries, see examples of John Harrison’s four marine chronometres and the bright red Greenwich Timeball, which served ships on the Thames and still drops daily at 1pm. Find out about the history of the speaking clock, and the story of George Airy, seventh Astronomer Royal, who pioneered an electrical system, spreading time from Greenwich throughout Britain via railway stations and telegraph lines.

Family events include “All the time in the world”, an introduction to the Observatory’s history with a costumed guide for ages eight upwards, August 28-30, September 11,12,18,19,25 and 26; and “Time with the stars” activity trails. Admission: pound;5 adults, pound;4 concessions, children five to 16 free; combined site ticket (with the National Maritime Museum): pound;9.50 adults, pound;7.60 concessions. Tel: 0208 312 6608; website: www.rog.nmm.ac.ukmuseumindex.html The countdown to the year 2000 and the count up to January 1, 2001, the start of the new Millennium itself, is being measured by Accurist’s Millennium Countdown Clock, positioned on the Meridian Line in the Royal Observatory, Greenwich, London SE10. To mark the beginning of the new century, the neighbouring National Maritime Museum is mounting The Story of Time, December 1, 1999 to September 24, 2000. It will look at our relationship to linear and cyclical time throughout history and current perceptions about time and space from around the world. New technologies and how these will affect people’s lives will also be explored.

The major themes are: the creation of time (how did the world begin? Creation myths); the mechanics of time (how different cultures have divided time and the tools that have been used to measure it - from the sundial to the atomic clock); the experience of time (biological time patterns, the ageing process, mythology and concepts of time); the depiction of time by artists; and the end of time (universal, apocalyptic and personal). Open 10am-5pm daily. Admission: pound;7.50 adults, pound;6 concessions, children five to 16 free. Combined site ticket as above. Tel: 0208 312 6608; website: www.nmm.ac.uk Explore the mechanical development and admire the beauty of the clocks and watches in the horology department at the British Museum, London WC1. The exhibits in Room 44 start with the simplest medieval weight-driven clocks and explain how they work, with text and diagrams. Tel: 0171 636 1555.

The medieval clock at Salisbury Cathedral is the oldest in Britain, dating from 1386. It has neither hands nor a dial as it was meant only to strike the hours. Wells Cathedral has a splendid clock dial which kept time until 1835, but the works are now in the Science Museum, London SW1. Both clocks are said to have been constructed by Peter Lightfoot.

The Royal Observatory of Edinburgh has hands-on exhibits and allows visitors to explore CD-Roms on space and astronomy. Open 10am to 5pm, Monday to Saturday, 12 noon to 5pm, Sunday. Admission: pound;3 adults; pound;2 childrenconcessions; pound;7 family ticket; group rates available. Tel: 0131 668 8405.

The Museum of the History of Science, the Old Ashmolean, Oxford, has an impressive collection of astrolabes, sundials, quadrants and early mathematical instruments including those used for astronomy and navigation. It is open 12 noon to 4pm, Tuesday to Saturday. Free admission. Tel: 01865 277280.

The general public first heard Big Ben’s distinctive bongs on BBC radio when they greeted New Year 1924 and until recently were heard every evening heralding the start of ITV’s “News at Ten”. According to the clock guide at the Houses of Parliament, this is “the most powerful and accurate public clock in the world” (Big Ben, incidentally, is the name of the bell, not the clock). Visitors can climb the 334 steps of the tower to marvel at the clock mechanism controlled by a pile of old coins, and listen to the sound of the bell striking. Write to your Member of Parliament at the House of Commons, London SW1A 2PW. Tours are free, but numbers are limited.

One of the most remarkable clocks in the world is Orloj, the astronomical clock on the south side of the Old Town Hall in Prague, Czech Republic. It was constructed circa 1410 by the clockmaker Mikulas of Kadan and the astronomer Jan Sindel. The 12 apostles show themselves two by two in two windows which open every hour. A skeleton rings a bell, turns over an hour-glass and nods at a Turk and the Turk shakes his head, explaining he does not want to go with him. Greed weighs his purse in his hand and Vanity admires himself in a mirror. The day of the month can be determined from a triple circle turning around a coat of arms of the Old Town in the middle and there is a zodiac calendar at the bottom. For details of holidays, contact the Czech and Slovak Tourist Centre, tel: 0171 794 3263.

WEBSITES

What’s the time? Such a simple question - but if you have access to the Internet, you’ll quickly find there’s no simple answer.

The search for an accurate time-check might begin at the Greenwich 2000 Time Channel at www.time.greenwich2000.com, the self-proclaimed “Home ofWorld Time”.

Here you will find a handy guide to world time zones, complete with their military designations (by which, mysteriously, London runs on Zulu time, while New Zealanders set their watches to Yankee). There’s also a detailed encyclopedia of the world’s great watchmakers.

It turns out that the all-important clock on the Greenwich home page is sourced from the US Navy’s Time Service Department in Washington DC (http:tycho.usno.navy.mil), keepers of the “Master Clock”. So is this the true source of the right time?

Maybe not. A link leads to the Time and Frequency Division of the National Institute of Standards and Technology (NIST) in Boulder Colorado (www.bldrdoc.govtimefreqindex.html), the keeper of time and frequency standards for the US. You can check your computer’s time clock against NIST’s online Atomic clock - but what’s this? “The uncertainty of the java clock is q1 second due to network delays.”

If NIST can’t do it, no one can, but this website makes a very good job of explaining the evolution of time measurement on its educational site, “A Walk Through Time” (http:physics.nist.govGenIntTimetime.html). Here we learn how the Egyptians, following their observations of the dog star Sirius, devised the 365-day calendar “that seems to have begun in 4236BC, the earliest recorded year in history”.

But that’s a mere eyeblink compared to geological time, which is explained concisely at the Web Time Machine (www.ucmp.berkeley.eduhelptimeform.html). This confirms that we now live in the holocene period of the quaternary part of the Cenozoic Era, which began 65 million years ago. The chart goes back as far as the Hadean period of the Pre-Cambrian Era (ie, 4,500 million years back). What was there before that?

Who better to ask than Professor Stephen Hawking? Go to his personal website (www.damtp.cam.ac.ukuserhawkinghome.html), where there’s an entertaining, mind-stretching essay, ‘The beginning of time’, in which he concludes that time started around 15 billion years ago, and will continue for “much more” than another 15 billion years.

All that time, but we’re trapped in the present. Try another Hawking site, Stephen Hawking’s Universe, at www.pbs.orgwnethawkinghtmlhome.html for serious discussion on the theme, “is time travel possible?” The Time Travel Research Center at www.time-travel.com shows just how much effort people who want to believe in time travel will expend to convince the rest of us that it is “a proven fact”, kept from us by nervous governments.

If you do go time-travelling, which calendar will you use? Boring old Gregorian, the distinctly upper-crust Julian, the complex Jewish calendar, or the sexy French Revolutionary system? You can chop and change between these systems at the “Calendar Converter” at www.genealogy.orgscottleecalconvert.cgi Time in the sense of the thing that trains do not always run to is handled with great efficiency at the Railtrack website (www.railtrack.com). The online timetable enables you to plan complex journeys in seconds. If only the trains themselves were so good.