Thinking too hard about jet lag
June 3, 2018 10:54 PM   Subscribe

When crossing the international date line, does that change which "direction" you're going?

Most tips on avoiding or minimizing jet lag mentions different advice depending on whether you're traveling "eastbound" or "westbound". At least once a year, I make a round-trip flight between Japan and the US. When I fly Japan → US, technically I'm going east over the Pacific, but since I cross the date line, I land the same day I leave. Would I follow "westbound" advice? (And the opposite for returning to Japan?)
posted by lesser weasel to Travel & Transportation (10 answers total) 1 user marked this as a favorite
I travel a lot internationally over long distances. My plan is to look at what time it will be when I land and try to adjust once I'm on board. If I land first thing in the morning then I sleep as much as I can on the flight and wake up when they do breakfast service. If I arrive in the late afternoon or night then I try to stay up as long as I can during the latter majority of the flight. It doesn't really matter which direction I'm going. This always works for me.
posted by joan_holloway at 11:32 PM on June 3, 2018

Jet lag is caused by your body's internal clock being out-of-sync with the local clock where the body physically is. (That, plus the effects of being enclosed in a tube for hours with limited food, water, exercise, fresh air.) So it's 1 PM where you are and where society expects you to be out and about but to your body's rhythms it's 10 PM and time to start generating those sleepytime hormones or whatever. There is no lag effect where your body's internal calendar thinks it's June 3rd but it's actually physically June 4th (or vice versa), you don't have a calendar that precise.

So eastbound travel is eastbound travel, independent of any date line. And I suspect individual variations (eg morning and night people, travel for business versus to go to a concert, people who can sleep on planes versus those who can't) overwhelm eastbound/westbound.
posted by Homeboy Trouble at 11:33 PM on June 3, 2018 [2 favorites]

Yeah, your body knows what time it expects the sun to come up, but not what the calendar is supposed to say. So if you're going east, you're going east.
posted by aubilenon at 11:48 PM on June 3, 2018

To clarify, I've done a lot of reading on managing the problem of jet lag as a subject, and I basically do what joan_holloway mentioned; but my question is more how to apply the directional-specific advice in what I read to my own situation.

For example [WaPo link]
"Jet lag’s severity depends on several factors, the most obvious being how many time zones you crossed. But which direction you traveled matters, too. Turns out, it’s not my imagination: Going east really does produce worse jet lag."
So many of these articles read like math problems. I know -- from personal experience -- that the more time zones I cross the worse it is. (Thank you, one full month of jet lag-based illness.) But:
"When you travel west, you gain several hours, so your day is extended and your body gets the extra time it naturally wants. But when you travel east, your day is shortened; that makes it harder to adjust, Jain says, because your body has to cut its natural cycle even further."
I am assuming the author is not crossing the international date line, because traveling EAST (Japan to US) definitely lengthens my day, while in the sentence above that's considered traveling WEST (landing on same day that I leave).
posted by lesser weasel at 12:03 AM on June 4, 2018

aubilenon says it best.

Jetlag happens because of disruption to your sleep/wake cycle. Yes, you go back a day when you travel east from (say) Japan to the US. Yes, that means that a specific calendar day is experienced for longer than it otherwise would be, despite the eastward travel. But no, your body clock doesn't know anything about whether it's the 3rd or 4th of June and just cares that the sun is up when it's not supposed to be and that it's having to walk around during sleep time.
posted by Urtylug at 2:27 AM on June 4, 2018 [2 favorites]

The rule of thumb is for every 1 hour of difference, you need 1 day to adjust. So you go one hour east, one day. One hour west, same deal.

I flew from Australia to Hawaii. Melbourne is 20 hours ahead of Hawaii, but it didn't take 20 days to get me to move my body clock- my body didn't care that breakfast was 4 hours different and also technically yesterday.
posted by freethefeet at 3:46 AM on June 4, 2018 [1 favorite]

I think once you get to ten or twelve hours of lag your body doesn’t much care what direction you’ve gone, because it’s very hard to interpret that as a “long day”. So for instance the with the difference from Hawaii to Japan vs Japan to Hawaii, the East vs West thing is in play. But with New York to Japan vs Japan to New York, the timing of your flight relative to your natural sleep time probably matters more than the direction. The date line is irrelevant though, unless you plan your flights a specific way to avoid losing a day.
posted by mskyle at 4:16 AM on June 4, 2018 [3 favorites]

it's not about the direction you travel or about the calendar day, it is about whether the next sunset/sunrise comes sooner (traveling "east") or later ("west") than your body expects it to.
posted by Rock Steady at 7:15 AM on June 4, 2018 [10 favorites]

It's way easier to stay up late and sleep in than go to bed early and wake up early.
posted by St. Peepsburg at 10:47 AM on June 4, 2018

The circadian rhythm is a little longer than 24 hours, more like 25 or 26 based on studies done with blind people who don't "reset" every day like sighted people do. That's why going west is a little easier.

The international date line is barely 100 years old whereas your pineal gland is a few million years old. (Well, not yours specifically, but the ur-pineal gland). When you cross the international date line, your pineal is basically like, "Damn meridians, get off my lawn!" and goes on secreting melatonin any old how.
posted by basalganglia at 4:33 PM on June 4, 2018

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