From the wikipedia:

The condition is not linked to the length of flight, but to the transmeridian (i.e., east-west) distance traveled. Hence, a ten-hour flight between Frankfurt and Johannesburg (going south, staying roughly on the same meridian) is less inducive of jet lag than a five-hour flight between New York and Los Angeles (going west). Also, the International Date Line should not be confused as contributing to jet lag, as the maximum possible disruption is plus or minus 12 hours. If the time difference between two locations is greater than 12 hours, subtract that number from 24. (For example, a 20 hour time difference equals 4 hours of jet lag).


>Again, like half a day so keeping in synch - sort of ?
>
>>I am pretty good with jetlags either way, but there is 13-hours difference between Sydney and Halifax.
>>
>>>Mmmmm, close to a day so probably not much change. I'm not sure that it's not the West->East that buggers you or t'other way.
>>>
>>>
>>>>While you are talking jetlags and such, here I am sitting at work - just arrived at 2:00 AM after 25 hours trip from Australia. :)
>>>>
>>>>
>>>>>When I went to HK years ago, I've no idea HOW long I was travelling, as we had to change planes in the UAE, then Bangkok, and the clocks were continuously going forward. Got into HK in the evening and was so tired I was close to tears. But as I only had 5 nights there I couldn't get my head down - had to get out on the streets.
>>>>>
>>>>>>The first time I went to Europe I was exhausted when I got there and went to sleep as soon as I had checked into the hotel. The two times I've been back since then have gone without problems. Coming back everytime, I was wiped out.
>>>>>>
>>>>>>>I do have more problems going west, esspecially if the time difference is about 8 hours or more. Going to the west coast is always challenging. Getting back home (flying east) rarely is a problem: I can take a nap any time of day.
>>>>>>>
>>>>>>>I just came back from Washington DC on sunday and appart from getting awake in the middle of the night and needing a dooze during the day I'm fine. However I do remember my first and second time at the west coast. I was shaking just like I had a severe fever and could not sleep at night at all for the first three days.