I've never experienced a sleeping pattern like this one. Biggest time difference I've ever done is +8 hours, which is most of SE Asia and even then only Japan was an issue with sleep, where it took me about 6 days to get into a decent pattern. When we stayed in Iniala (was either +7 or +8 hours at the time) it took 1 night in Singapore and I was fine. Since flying to Sydney (+9 and then +11 for Fiji) I've not slept past 4am a single night, even when going to bed at 1am.