I used to think jet lag was just about feeling groggy for a day or two.
Turns out, your circadian rhythm—that internal clock ticking away in your suprachiasmatic nucleus, a tiny cluster of maybe 20,000 neurons tucked behind your eyes—doesn’t just reset because you landed in Bangkok. It’s stubbornly anchored to your home time zone, and every cell in your body is basically screaming conflicting schedules at each other. Your liver thinks it’s 3 AM. Your cortisol production is convinced it’s noon. Your melatonin receptors are just… confused. I’ve seen travelers pop melatonin supplements like candy, thinking it’ll fix everything, but here’s the thing: melatonin isn’t a sleep drug, it’s a timing signal. Taking it at the wrong time can actually make jet lag worse, pushing your clock in the opposite direction you need. The half-life is roughly 20 to 50 minutes, give or take, so timing matters more than dosage.
The Light Exposure Window That Actually Matters (And Why Your Hotel Curtains Are Sabotaging You)
Light is the most powerful circadian reset tool we have. But not just any light at any time.
If you’re traveling east—say, New York to Paris—you need morning light at your destination to shift your clock earlier. Sounds simple, except most people do the exact opposite: they arrive exhausted, draw the blackout curtains, and sleep until 2 PM local time. Then they’re up all night wondering why they can’t adjust. Wait—maybe the problem is that our instincts are backwards here. When you’re exhausted, your body wants darkness and rest, but what it actually needs is a bright slap of daylight between 6 AM and 10 AM local time, even if you only slept three hours on the plane. I’m not saying it feels good. It feels terrible, honestly. But exposure to roughly 10,000 lux of outdoor light (not through a window—glass filters out the specific wavelengths your photoreceptors need) for 30 to 45 minutes can shift your clock by an hour or more per day.
Traveling west is theoretically easier because you’re staying up later, which most people can do naturally. The trick is avoiding light in the early morning at your destination—those first few hours after dawn will anchor you to the new time zone before your body’s ready. Some travelers wear blue-blocking glasses in the morning, which sounds ridiculous until you realize that your melanopsin-containing retinal ganglion cells are most sensitive to blue wavelengths around 480 nanometers. Block that, and you’re essentially telling your brain it’s still dark out.
The Messy Reality of Pre-Adjusting Your Schedule and Why It Probably Won’t Work Anyway
Every travel article tells you to shift your sleep schedule before you leave.
In theory, if you’re flying to Tokyo from Los Angeles, you’d start going to bed an hour earlier each night for a week beforehand, gradually aligning yourself with Japan Standard Time. In practice, this rarely works because—and I guess this should be obvious—you’re still living in Los Angeles. Your work schedule, your social commitments, your family meals, the fact that the sun is still setting at 7 PM… all of that keeps pulling you back. I used to try this religiously before international trips, and I’d just end up sleep-deprived at home AND jet-lagged abroad, a double punishment for trying to be proactive. Honestly, the research on pre-adjustment is mixed anyway. Some studies show benefits for shifts of three time zones or fewer, but beyond that, you’re fighting biology. Your circadian system can only shift about an hour to maybe 90 minutes per day maximum, so if you’re crossing eight or nine time zones, you’d need to start adjusting more than a week in advance, which most people simply cannot sustain without wrecking their current life.
There’s also the issue of social zeitgebers—that’s the fancy term for social cues that reinforce your schedule. Meal times, work meetings, when other people are awake and talking to you. These matter almost as much as light. If you’re trying to sleep at 8 PM in Paris but your colleagues keep texting you during what’s their afternoon (your theoretical night), good luck keeping that schedule consistent. The environment wins, usually.
One approach that does seem to help: strategic napping. Not long naps—those drag you deeper into your home time zone—but short 20-minute power naps timed carefully. If you’re fighting afternoon fatigue after crossing westward, a brief nap around 2 PM local time can take the edge off without derailing your adjustment. Any longer and you’ll wake up groggy and more confused than before, something called sleep inertia, which can last 30 minutes or more depending on how deep you went.
The other weird factor nobody talks about: individual chronotype. Morning larks adjust to eastward travel better. Night owls handle westward better. If you’re naturally someone who stays up until 2 AM, asking you to suddenly thrive on a Tokyo schedule (where you’d need to be asleep by 9 PM to wake up at 5 AM local) is like asking a cat to enjoy swimming. It might happen, but it’s gonna be a struggle. Some people also just… don’t get jet lag as badly. Genetic variations in clock genes like PER3 seem to play a role, though the research is still figuring out exactly how. I’ve traveled with people who bounce back in a day, while I’m still a zombie on day four, and we ate the same meals, saw the same light, took the same flights. Biology is annoyingly unfair like that.
Anyway, if there’s one thing I’ve learned after maybe a dozen long-haul trips, it’s that perfection is impossible. You’re going to feel weird and off-kilter for at least a few days. The goal isn’t to avoid that entirely—it’s to minimize the damage and not accidentally make it worse by doing the exact opposite of what your circadian system needs, which is surprisingly easy to do if you’re just following your instincts.
