New Zeeland is + 12 hours from GMT, the east coast of Aus (Sydney, Canberra etc.) is +10 hours, dunno for Darwin etc. as they are much further west. But if you know the time difference from say Sydney -> Darwin you can just calculate it.
But, now, during Daylight Savings, the UK is not on GMT, they are GMT + 1, Sweden (Central European Time) is GMT + 2 so it's a bit hard.
But let's say 1500 hours Saturday in London, that makes it 1600 hours CET (Me!), and 0300 hours Sunday in New Zeeland. If you're in Aus (Sydney-ish) it would be 0100 hours Sunday.