Since we mainly travel east-west rather than north-south, Zoe has been through more time zones than most 1 year old babies. On our first trip to Sweden when she was only 3 1/2 weeks this was the last thing on my mind because she hardly had any sleeping habits down for nighttime vs. daytime. I was right, she only stayed awake 4 am to 6 am for three nights, together with her equally jetlagged parents. Later on though, I started to worry and search for advice on the wonderfully informative internet. Most articles provided the same piece of advise that they give adults: try to get on the new timezone as quick as possible, but I could not find anything more concrete. Perhaps traveling with babies through timezones was just not that common and nobody really knew anything about it? It turns out that there is another reason few people write about it, which is that it simply isn't that difficult. As it turns out babies adjust to new timezones much quicker than the grownup and because the baby tends to travel with a grownup, who also has jetlag, the grownup's jetlag often takes mental precedence.
When I traveled to Scotland with Zoe on my own, at 6 months, she simply skipped her jetlag all together. When she woke up at night I fed her a bit and she rolled over to her other side and fell asleep again. I, on the other hand, lay awake for 2 hours in the early morning, staring at this magically sleeping baby next to me. When we went to Copenhagen for Christmas, just her and me for the first week, she woke up a couple of nights, scrabbling about in the big bed, clearly tired but unable to sleep, for an hour until she fell asleep on my arm or on my belly. In China when she was 10 months she simply woke up at 4 am for 3 mornings in a row; since I was awake as well we went into the giant bathroom of our hotel room, not to disturb Mark who did not have jetlag, and played until breakfast started at 6 am.
Well, I do have a disclaimer, because I think I have lucked out so far and I am not looking forward to a jetlagged 15 month old when we travel to London in the end of August. Two key things helped: breast feeding and bed sharing. Zoe could always be calmed down by a little 'midnight snack' and she could fall asleep again, right there next to me, while eating. She is now too big to sleep in the same bed as me, mainly because she goes to bed 4 hours before me and is so mobile that I am worried she would fall down, but also because she loves spreading out and a double bed is only a double bed, not a triple bed. But given those two 'secrets', jetlag before 1 was not that bad.