Westward jet lag is the easier direction to recover from, but it still hits hard if you cross enough time zones. Your body can naturally shift about 1.5 hours later per day when traveling west, compared to only 1 hour per day when going east. That means a flight from New York to Honolulu (crossing five time zones) takes roughly three to four days of full adjustment. The key to speeding that up is working with your body’s preference for a longer day, not fighting it.
Why Westward Travel Is Easier on Your Body
Your internal clock runs on a cycle slightly longer than 24 hours. When you fly west, you’re essentially asking it to stretch the day out, which aligns with its natural drift. This is called a phase delay: your sleep-wake cycle needs to shift later to match the new time zone. Flying east forces the opposite, a phase advance, which is harder because you’re compressing the day against your clock’s tendency.
That 1.5-hour-per-day adjustment rate is the average for people who don’t take any special steps to manage light or sleep timing. With deliberate strategies, you can push that rate faster and feel functional sooner.
The Symptoms You’ll Notice
Westward jet lag typically shows up as waking far too early in the new time zone. Your body still thinks it’s morning when the local clock says 3 or 4 a.m. You may also crash with heavy fatigue in the late afternoon or early evening, well before a normal bedtime. Other common symptoms include trouble concentrating, digestive issues like constipation or diarrhea, and general irritability or low mood. These usually start within a day or two of arrival and get worse the more time zones you’ve crossed.
Use Evening Light to Push Your Clock Later
Light is the single most powerful tool for resetting your internal clock. When traveling west, you want to delay your rhythm, and the way to do that is by seeking bright light in the evening hours at your destination. Stay outdoors or in well-lit environments during the late afternoon and evening for the first few days after arrival. Sunlight is ideal, but bright indoor lighting works too.
Just as important: avoid bright light early in the morning for the first couple of days. Early morning light sends your clock in the wrong direction by advancing it. If you wake up before dawn at your destination (which you will), keep the lights dim and wear sunglasses if you go outside before mid-morning. Once your body starts waking at a more appropriate hour, you can relax this rule.
For trips crossing more than six or seven time zones westward, be cautious. At that point, the direction of your light exposure can backfire. Evening light at your destination might actually fall during your body’s “advance” window rather than its “delay” window, making things worse. If you’re crossing eight or more zones, treating the trip as if you flew east (and advancing your clock instead) sometimes works better.
Shift Your Meals to Local Time Immediately
Your brain’s master clock responds primarily to light, but the clocks in your liver, pancreas, and gut respond primarily to when you eat. Animal research shows that scheduled feeding can reset these peripheral clocks independently of light exposure, with the liver clock in particular treating meal timing as its dominant cue. This means eating breakfast, lunch, and dinner at local times from the moment you land helps pull your digestive system onto the new schedule, even before your sleep cycle fully catches up.
If you arrive in the evening and aren’t hungry, eat a small meal anyway. If you wake at 4 a.m. starving (because your stomach thinks it’s lunchtime back home), have a light snack but save your real breakfast for a normal local hour. The goal is to stop reinforcing your old schedule with food cues as quickly as possible.
Time Your Exercise for the Evening
Physical activity shifts your circadian clock in a predictable, time-dependent way. Research on human phase response curves shows that exercise performed between roughly 7 p.m. and 10 p.m. induces a phase delay, exactly what you need after flying west. Morning exercise between 7 and 10 a.m. does the opposite, advancing your clock.
So for your first few days at your western destination, schedule your workouts, runs, or even brisk walks for the evening. It doesn’t need to be intense. Even moderate activity during that window reinforces the “stay up later” signal you’re trying to send your body. Avoid hard morning exercise until you’ve adjusted, since it works against your goal.
Use Caffeine Strategically
Caffeine does more than keep you alert. A double espresso consumed three hours before your usual bedtime delays your internal clock by about 40 minutes, according to research from the University of Colorado. When flying west, this effect actually works in your favor during the first couple of days. A coffee in the late afternoon at your destination can help you push through the evening fatigue that hits when your body thinks it’s bedtime back home.
The catch is knowing when to stop. Once you’ve shifted enough that you’re staying up until a reasonable local bedtime, late caffeine starts working against you by making it hard to fall asleep. A good rule: use afternoon caffeine on days one and two to power through the evening slump, then pull your last cup back to midday as you settle into the local rhythm.
Melatonin Works Differently Going West
Melatonin is widely recommended for eastward travel, where you take it at bedtime to advance your clock. Going west, the picture is less straightforward. To delay your clock with melatonin, you would need to take it in the morning, which is counterintuitive and can cause drowsiness right when you need to be functional. Most sleep researchers consider melatonin less useful for westward trips than for eastward ones.
If you do want to use it, a low dose (0.5 to 3 mg) taken at your new local bedtime can help you fall asleep if you’re lying awake, but it’s acting more as a mild sleep aid than a clock-shifting tool in that scenario. For most westward travelers, light management and activity timing deliver better results.
What About Blue-Light Blocking Glasses?
Blue-light blocking glasses have gained popularity as a jet lag tool, but the evidence is underwhelming. A study at the University of North Carolina found no significant difference in sleepiness levels between travelers who wore blue-light blocking glasses and those who didn’t. The glasses group did report slightly less negative mood, possibly from melatonin released when blue light was filtered out, but the core problem of jet lag (misaligned sleep) wasn’t improved. You’re better off controlling your actual light exposure, getting outside in the evening and staying in dim environments in the early morning, than relying on glasses to filter specific wavelengths.
A Practical Day-by-Day Plan
For a westward trip crossing four to six time zones, here’s what a solid adjustment strategy looks like:
- Day of arrival: Eat dinner at the local time even if you’re not hungry. Stay in bright environments until 9 or 10 p.m. local time. Resist the urge to go to bed at 7 p.m. A late afternoon coffee can help.
- Day one: You’ll likely wake between 3 and 5 a.m. Keep lights dim and avoid going outside until mid-morning. Eat meals on local time. Exercise in the evening. Seek bright light from late afternoon through the evening.
- Day two: Your wake time should shift an hour or two later. Continue the same light and meal strategy. You can start relaxing the morning light avoidance.
- Days three and four: Most people crossing four to five zones feel close to normal by now. Resume your usual routines.
If you’ve crossed seven or more zones, expect this timeline to stretch. At roughly 1.5 hours of adjustment per day, a ten-hour time difference takes close to a week without intervention. The same principles apply, they just need to be followed more consistently and for longer.
Start Shifting Before You Leave
If your schedule allows it, you can begin delaying your clock two to three days before departure. Go to bed an hour or two later than usual each night and sleep in a bit longer. Seek bright light in the evening and keep mornings dim. Even a one to two hour pre-shift reduces the gap your body needs to close after landing, which is especially valuable for longer westward trips.