Apparently the day is supposed to be the one half way between the autumnal equinox and the winter solstice. Groundhog Day is the other one, and falls half way between the winter solstice and the vernal equinox.
That makes April 30 Hallowe'en here, August 1 is Groundog's Day, November 1 is May Day (that would be November Day), and Feb 2 Lammas whatever that is.
Well, we don't have Groundhogs in Australia, but we do have a burrowing animal: the wombat. That makes August 1 Wombat's Day.
From now on I will be celebrating Wombat's Day.