Gmail contacts birthdays wrong in WP7

[dub.survivor]

I think that is might be something to do with being in the New Zealand time zone, but sometimes birthdays I have set in my Gmail contact list that get synced to my WP7 are out by a day.
I don't know who the culprit is whether it is Microsoft or Google, but I think it mainly happens if editing details in a contact in gmail and it gets synced to the phone with the wrong date. Birthdays shouldn't be changed to compensate for time zones anyway!
I have the time zone in gmail calendar set to New Zealand (no option to set time zones other than in calendar that I can see). In google account settings -> Personal information, I can set a country but it won't allow me to change the time zone. I googled this and apparently it is set automatically to time zone on computer (which is New Zealand anyway)
Just interested to hear if anyone else has come across this issue, found what is causing it (is it timezone dependent) and found a solution?

Cheers

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