OccultForum.org

I've always had a lot more success with working with the actual placement of the stars/planets/etc then working with dates, times, and what not. So when I want to work with Mars, I go outside and look at Mars. He's right overhead? Good time to work. Even just adding "stargazing" into my personal practices had a strange effect of taking me off the "clock" so to speak and putting me onto the real clock of the universe. So maybe when its "cold" is just when its cold and not during some set dates that a book says.

That being said a quick google showed that there are a lot of pagans from Australia, for instance, and other areas in the southern hemisphere, that have published calendars and wheels appropriate to their location, as examples to come up with your own system that works.

Well, why do you celebrate something?
Because it's tradition? Then keep to the old dates.
Because you want to be in contact with the same mentality as those that created the tradition? Then adjust to your current location.

I'll page my fave NZ'er, this is something he'll understand and relate to.

Fire festivals are still there, just the 'wrong' way round, lol. Shoudn't be too hard to adjust, as you can be guided by locality as Des said.

Imbolc/ Lughnasadah

Ostara/ Mabon

Bealtainn/ Samhain

Yule and Missummer solstice, also. Of course. Big ones. Dark and light halves.

Christmas is a public holiday for most places anyway, keep it as is, I guess. Mine is secular but falls under Yule, so yay! Extra partaaay, mon the Scots, lol.

Midsummer celebrate when it happens, as with Yule.

Sounds like you have a good plan. You could also just be like all us Americans and drag out each and every holiday as much as you can, and cover both bases...lol