Can't wait for Christmas? Why not go abroad for your festivals instead? There is always something going on somewhere. Visiting festivals is not only a way of crashing other people's parties, it is also a way to see local people at their best and take great photos. If you don't lose your camera in the mêlée, that is.

Humans have been cluttering the calendar with special dates since the dawn of history. Some of these have never stopped, other new ones started up yesterday. Some are a fantastic spectacle; others offer nothing to see. If you are going halfway round the world to see one, make sure you have got the dates right.

Not that you need to go far. Every country in the world, perhaps every city, contains its own festivals, and Britain is no exception. Annual examples here include the explosive Guy Fawke's Night on 5 November, as well as curiosities such as the 300-year-old Shrovetide football match in Ashbourne, Derbyshire, in February.

Worldwide however, the origins of the oldest festivals revolve round agricultural rites, marking seasonal changes like the beginning of spring or the coming of the rains. Such festivals tend to follow the lunar calendar (lunar cycles were easier to count), which means that tourists have to check their calendars carefully. Given common agricultural origins, it is no coincidence that the end of winter is marked almost simultaneously in Europe and China by two of the world's largest festivals.

Carnival, which takes place on the days leading up to Ash Wednesday, 40 days before Easter, is a mad party throughout the Catholic world. Fat Tuesday or Mardi Gras is the climactic finale of these celebrations. In Europe, Mardi Gras is celebrated in all Catholic countries, but perhaps most famously in Venice, where harlequins and incognito strangers in chalk-white masks stalk the streets. Fantastically ostentatious fancy-dress balls are also held in Vienna at this time, while in the German city of Cologne, women run around cutting off men's ties.

Mardi Gras in the Americas is even more outrageous. In New Orleans bizarrely dressed paraders march to the accompaniment of an insane amount of bead- flinging, flambeaux-carrying, chanting and boozing. But even this is nothing compared to what goes down in Rio de Janeiro, probably the single most famous street party in the world, where the emphasis is heavily on transvestism, erotic costumes, scantily clad dancers and alcohol. Finally Sydney's Gay and Lesbian Mardi Gras parade (which actually falls a couple of weeks into Lent) is the latest spin-off from the Carnival scene.

By contrast to which, the end-of-winter festival at the other end of the Eurasian landmass - Chinese New Year - is altogether low key. Instead of street parties, this is a time for families to come together, the main consequence of which is closed restaurants and horribly crowded train stations. From the traveller's point of view, it is a time to avoid China. You will see more by hanging around for the lion-dance festivities in London's Chinatown.

Other festivals with ancient roots are to be found all over Asia. No Ruz, the Iranian new year marking the spring equinox, provides travellers with a fascinating glimpse into the ancient heart of Iran; apart from feasting, one age-old custom is for everyone to join in leaping over street bonfires. The symbolism of this comes straight from the pre-Islamic fire-worshipping cult of Zoroastrianism.

Hindu and Buddhist communities, in countries such as India, Nepal, Thailand and the Indonesian island of Bali, retain traces of ancient cults in virtually every town and village, to the extent that travellers need hardly consult their calendars to be sure of running into colourful festivities.

India is the country with the oldest recorded surviving festivals. In the north particularly, the beginning of spring is marked by a major festival, Holi, the Festival of Colour, during which people bombard each other with water and paint. In Bombay, the holiday Ganesh Chaturthi is dedicated to the Hindu god Ganesh, (late August/early September: check dates), and sees huge processions carrying images of the god to immerse in the sea. The whole country in fact gets through a lot of rampant celebrations at the end of the monsoons, ostensibly commemorating events from the great Hindu epic, the Ramayana.

In contrast to these ancient ceremonies, the holidays associated with the world's monotheistic religions represent attempts to modernise ancient festivals, to tie them into an up-to-date framework. It is not, for example, coincidental that Christmas falls at the time of the winter equinox, and Easter at the spring equinox. This probably reflects ancient Mediterranean beliefs in a god who is born at the coming of the winter rains, only to die again at the beginning of the summer heat.

Interesting though the myths may be, for the traveller Christmas is rarely more than a family affair outside Bethlehem and the Vatican in Rome, where huge crowds congregate to hear the Pope lead mass. Easter is a better time to travel: southern Spain, above all, celebrates Semana Santa (Holy Week) in flamboyant style, especially in the Andalucian city of Seville, where colossal processions of hooded, masked figures take place with figures of the Virgin Mary and Jesus being carted around in tow. Greek Easter, which follows some weeks later, is likewise an excellent time to be in Greece. Islamic festivals are widely observed in the religious sense, but are not exactly occasions for tourist gawping. Eid El Fitr (the breaking of the fast after the holy month of Ramadan) and Eid El Adha are big family occasions, though if you happen to be in an Islamic country at this time you may be invited to banquets involving the slaughter of goats.

The biggest Shiite festival is Ashura, commemorating the martyrdom of the Shiite hero Hussein, killed in the battle of Kerbala in 680 AD. This is an occasion for mourning and grief rather than celebration, with young men each competing to flagellate themselves more bloodily than the next. This can be seen in Iran and parts of Iraq and Lebanon, though tourists may not feel very welcome.

Jewish holidays are notable for their extreme frequency, and again, where travellers are concerned, these might not be the best times to actually visit Israel. Several of the holidays, notably Yom Kippur and Sukkoth, involve varying degrees of abstinence and self purification. Purim, on the other hand, (February/March-check dates) is an occasion for outright revelry - and it's the only chance you'll have to get drunk with orthodox Jews.

Moving away from ancient myths and religions, it is perhaps refreshing at the dawn of the twenty-first century to realise that festivals are not exclusively rooted in the remote past. In truth, most of us spend more time celebrating secular festivals than religious ones.

National holidays can be exciting occasions anywhere. Independence Day, the USA's birthday bash on 4 July is a great time to be around, with fireworks, music and large crowds gathering in towns and cities. France's Bastille Day, just ten days later on 14 July, is another patriotic extravaganza.

The secular holiday that comes nearer than any other to being a truly world holiday is 1 January. Huge crowds at places as diverse as the Vatican, Times Square, Trafalgar Square, the Brandenburg Gate and Sydney Harbour (to name but a few) spiritually unite for heavy drinking and singing of Auld Lang Syne, Robert Burn's song, which was composed to mark Scotland's own Hogmanay.

But the modern world's real contribution to the festival lies in the great sporting events of the twenty-first century: the football World Cup and, above all, the Olympic Games, two four-yearly events for which virtually the entire world comes to a standstill. Being able to attend either event in person is the equivalent - perhaps - of what a religious pilgrimage would have been in another age. Political occasions - the American elections spring to mind - can also make pretty good jamborees. If you are able to travel, it really can be Christmas every day.