Spring Down Under

Today is the first official day of spring in Australia (and also the first day it hasn't rained lions and wolves - like cats and dogs only heavier! - in a week, or do I mean a month?) It has been a ridiculously wet winter in Tasmania. Naturally three months ago all the 'experts' were saying to expect a very dry winter! Australian spring starts on 1st September, summer on 1st December, autumn on 1st March and winter on 1st June. As a British colony we would logically have inherited these dates from the English (only in reverse). So why do the British and American seasons officially change on the solstices and equinoxes? I can't seem to find an answer to this question, but I assume that someone 'up north' decided to change the dates of the seasons sometime after Australia was colonised (the past 200 years) but forgot to tell us. Pushing the official seasons back does make sense as the earth's wobble on it's axis and variations in it's orbit (etc) mean that the seasons have changed over time. Why, the winter solstice was once celebrated as 'Midwinter', but now it is only considered the start of winter rather than the middle. If anybody knows when and why it was decided that the northern seasons officially start on the solstices and equinoxes or why us Aussies are different, I'd like to know so please leave a comment!