Nine of the world's leading ski resorts - from Canada to Japan, and even the Cairngorm mountain above Aviemore in the Scottish Highlands - turn 50 this winter. Although spread widely around the planet, each began operating in autumn 1961, during a decade that saw an explosion of resort construction worldwide.
In some cases local authorities planned to revive dwindling rural populations caught in a post-war slump. In others, it was simply a case of a few enthusiastic locals wanting to make skiing their surrounding mountains an easier prospect. In every case (except, arguably, Aviemore) the resorts have since grown to become a leading player in world skiing.
Winter sports holidays can be traced back much further, of course. The 150th birthday of the first ever recorded, in St Moritz, Switzerland, in 1864, comes up in a couple of years. The invention of downhill skiing, which most of us practise on those holidays, passed its centenary in 2005.
However, it was the 1960s when the sport began to hit the mass market and when nearly half of the world's estimated 5500 ski areas were born.
Two resorts, one on each side of the Pacific, began life without much thought for the future. Fernie in Canada and Niseko in Japan were created simply because local people wanted to make the best of the snow. Fifty years on, both have achieved worldwide fame because of their abundant powder.
Fernie is probably the only resort that will offer a bigger vertical this winter thanks to a new chairlift, and Niseko is opting for a new gondola as its 50th birthday present to itself.
"Many of the early community members were avid powder-lovers and knew they had a very special place," says Matt Mosteller, who works for Fernie.
"When word leaked out, other powder-lovers arrived."
One of them was a Swiss instructor called Bruno Engler, who was to become a guide in Fernie.
"He said that Fernie had the best snow in the Canada and that it was sure to be a hit in world skiing."
In other cases, the plan was always to make it big, although perhaps the resort's originators never realised just how big.
La Plagne, for example, began with a couple of drag lifts, but now has more than 100 lifts of all types. Each year it attracts more than two million skiers to its 10 base villages.
La Plagne was one of the first of around 100 purpose-built, high-altitude French resorts. Most were built as part of an inspired post-war plan to revive the ailing French rural economy. The aim of the central planners was to make ski holidays much easier and more affordable.
Such was the success in France that this approach has subsequently been copied in mountainous areas worldwide.
Turkey, Russia and China all see ski-resort development in troublesome mountain regions as a way to bring economic and, they hope, political stability.
In Norway, Hemsedal was planned "as an international resort", according to Odd Holde from the tourist office. Not very international, mind you; the target nations originally were Norway, Sweden and Denmark.
Fifty years ago, the annual turnover was the equivalent of £27,000 (NZ$53,600).
Today, the business is worth £77m. And the urbanwards tide has turned: the local population has doubled to 2200.
Back in 1961, the development of the Breckenridge resort in Colorado, USA, was seen as a potential saviour of the town, where the population had dwindled to 300.
Ironically, one of the leading objectors to the plan was the team behind neighbouring Vail, which opened a year later and went on to buy Breckenridge.
Further north, in Canada, another 50-year-old ski area has changed its name over the past half-century.
What began as Tod Mountain is now Sun Peaks. It was originally planned by the local ranching community who hit on the idea of building the longest chairlift in North America for opening day.
The resort's current president, Christopher Nicholson, says: "In addition to the original Burfield chairlift, there was a very steep surface lift. Kids learned to ski very quickly in those days."
The resorts are celebrating on several levels. Many are announcing major infrastructure improvement projects, all of them are offering birthday parties and some special deals for visitors this winter.
Crested Butte in Colorado is giving free lift passes for use on its birthday (November 23) - or on yours if it happens during the ski season and you're there. You don't have to be 50, but you will need proof that it is really your big day.
La Plagne has announced plans for a precise €8,780,100 (including VAT) three-year beautification project that will see much of its 1960s concrete transformed in to something thoroughly modern.
In Scotland, the Ski Age began for Aviemore in 1961 with the installation of the first lift at Cairngorm mountain above. Planned celebratory events include a re-enactment of walking from Glenmore Lodge to the summit, possibly in tweeds, as the pioneers did before that first lift was built.
WHO WERE THESE EARLY SKIERS?
At the start of the 1960s, winter-sports holidays were still largely the preserve of the wealthy classes. By the end of the decade, far more people could afford to ski. This was thanks to the boom in resort construction, improving road and air links, and the efforts of package-holiday companies, particularly in the schools market.
One British operator that was around in 1961 and has survived today is Inghams. Another is the pioneering firm, Erna Low, which by the Sixties had already been offering ski holidays for three decades.
Joanna Yellowlees-Bound is now the chief executive of the company.
"In the early 1960s, Erna Low was in its heyday," she says.
"The formidable Miss Low was selling holidays all over the world. Most people travelled by rail from London Victoria in those days with a 24-hour trip to Austria."
Mirroring the financial turbulence of today, it was a difficult period - made tougher by foreign-currency exchange controls, which Miss Low - in common with other tour operators - found various ways around.
As the ski market matured in the 1970s, ski-resort construction slowed dramatically. Since the 1980s only a few new resorts have opened each year, these days mostly in Asia. However, fears that skiing itself could die out, as snowboarding took over, were misplaced.
Snowboarding (which hits its own big three-zero watershed in 50-year-old Stratton, Vermont this winter) was new and cool.
The average age of skiers was 39, and going up a year every year as the next generation opted to snowboard.
But skiing re-invented itself with shorter, easier-to-use skis replacing the long, straight style that had endured for most of the 20th century.