PARIS, Milan, New York, London: all observe two fashion seasons each year - and so at long last will Hong Kong. ''September 2-5 will be the dates for the first spring-summer Hong Kong Fashion Week,'' Owen Chi, assistant executive director of the Trade Development Council, revealed on Monday. ''We considered holding the fair in July, but after doing a survey, we decided on September,'' he said. ''When we see the results, we'll know if we made the right choice. ''Like our January fashion week, it will be held at the Convention and Exhibition Centre, though smaller in scale.'' Why has it taken Hong Kong more than 20 years to fall into line with the rest of the fashion world? In a nutshell, economics. ''The simple fact is that autumn-winter garments command a higher price on the international market than those for spring-summer and understandably, local manufacturers want to make the most of their quotas,'' Mr Chi said. ''On the other hand, you can't do just one season if you want to promote fashion properly, especially if you've positioned yourself as Asia's fashion capital. ''I've always thought we needed a supplement to our January fashion week. In fact I did a survey as early as 1987 and though the reaction was mixed, we decided to hold a spring-summer pavilion at Fashion Week '88. ''The response wasn't too bad. About 30 to 40 companies took part and we even had a group from Australia showing beachwear.'' Encouraged by the experiment, the TDC decided to launch Hong Kong's first fully-fledged spring-summer fashion fair in July 1990. It never got off the ground. In the wake of Tiananmen Square, came global recession and the fair was cancelled through lack of support. Then came the Gulf War - the bombs were dropping on Iraq just as Hong Kong Fashion Week '91 began - but Mr Chi never abandoned his pet project. ''Timing; that's always the crucial thing,'' he said. ''We just had to wait till the right elements came together and I believe that has now happened. ''The biggest change in the world economy is that while the United States and Europe have remained depressed, other markets have come up strongly - especially Southeast Asia. ''Take Thailand whose import duties used to be almost 100 per cent and which is now aiming to get them down to only 20 per cent; or Taiwan, which is going the same way. ''There's a lot of spending power in Asia and when you examine its population profiles - all those young consumers with money - and compare them with the ageing West, you can see how things are shaping up.'' The climate is also right for Hong Kong's first spring-summer fashion week in a literal sense. As Mr Chi happily points out, millions of those upwardly-mobile young consumers live in countries where it's hot virtually all year round. ''Thailand, Malaysia, Singapore, the Philippines, Indonesia - none of them are interested in autumn-winter and I believe we can also attract a lot of interest in the southern hemisphere, with its reverse seasons. ''Initially, we hope to have about 20 per cent of our exhibitors from overseas, though our key aim is to recruit local exhibitors of the highest calibre. ''Hong Kong at the forefront of fashion - that's the image we want to promote in September. ''We hope to have 150 to 200 exhibitors. That may be modest compared with the 814 we had at Fashion Week in January, but you know the saying: Rome wasn't built in a day.''