'Tis The Season...

Today is the first day of winter.  For some who live in other parts of the world this may seem strange.  After all, for those in the Northern Hemisphere the short days of winter are becoming a memory as you look forward to summer.  However, if you were schooled in the same way as I you will not officially announce summer until June 21st.  If the seasons between the Northern and Southern hemisphere are opposite, then it would seem logical that winter would start on the same date.  So why am I announcing the arrival of winter on the 1st of June?
Since moving to Australia I have learned that even though the calendar is divided into the same four seasons as other parts of the world,  the "official" start date does not coincide with the equinox or solstice.  Instead, here in Australia the change of the season is marked on the 1st day of  December, March, June and September for the start of Summer, Autumn, Winter and Spring, respectively.
So once again my cross-cultural experience has taught me that even though internationally in temperate zones seasons are divided into 3 months and have similar characteristics--amount of daylight and temperatures--, the actual start and end date varies across the globe.