Jet Lag From Los Angeles to Sydney and Auckland: You Lose a Day, Not Your Body Clock

Why this route is hard

Start with what this route is not. Los Angeles to Sydney is not a 17 hour shift, whatever the clocks say. A body clock moves by the shortest path, and 17 to 19 hours ahead is the same as 5 to 7 hours behind. The Jet Lag Calculator resolves the trip as a westward delay, bedtime moving later, which is the direction the clock drifts on its own and the easiest kind of jet lag there is. Many articles describe this route as an eastward shift because the plane flies west across the date line into tomorrow; the tool, and the research it is built on, count the hours the other way.

The season decides the size, and on this route it swings more than anywhere else, because the two hemispheres change their clocks in opposite directions. From November to March, Sydney is on daylight time and Los Angeles is not, and the delay is 5 hours. From April to October it flips and the delay is 7 hours. For a few weeks around the changeovers it is 6. Auckland runs 2 hours further ahead than Sydney, which brings it closer to inverted and makes the shift smaller: 3 hours in the US winter, 5 in the US summer. Melbourne shares Sydney's clock.

So what makes the route hard is not the clock. It is the flight. Los Angeles to Sydney is 15 hours, leaves late at night, and lands in the early morning two calendar days later. You lose a night's sleep, or most of one, and a day off the calendar, and arrive tired in a way that feels like jet lag but is mostly sleep debt. Going home, the flight leaves Sydney in the morning and lands in Los Angeles the same morning, which gives the day back but turns the 5 to 7 hours into an advance, the harder direction.

The plan treats the two legs differently: a short, easy shift out that mostly needs you to sleep early and get daylight, and a longer one home that needs prep nights.

Flying out

Enter your route in the calculator and it produces a plan in three parts: prep nights before you fly, the flight, and arrival days. Here is what it does for Los Angeles to Sydney with two prep days and a usual bedtime of 10:30 PM, in both halves of the year. Melbourne is identical; Auckland runs 2 hours smaller.

Prep nights. Each prep night moves bedtime an hour later: 11:30 PM two nights before, 12:30 AM the night before, with wake time sliding later to match. Evening light pushes the clock later; a dim first hour after waking stops the morning pulling it back. Two prep nights take two hours off the shift, which on the 5 hour version of this route leaves only three to do on arrival.

The flight. No scheduled sleep window on the plan, but on a 10 PM departure the first half of the flight is your normal night, so sleep as early as the cabin allows. A nap later in the flight is fine if it stays under two hours; you want to land tired enough to sleep early in Sydney. Alcohol fragments whatever sleep you get.

First night in Sydney. From April to October, on the 7 hour version, the plan's first sleep window runs 7:15 PM to 3:15 AM Sydney time. From November to March, on the 5 hour version, it runs 9:15 PM to 5:15 AM. Both are early by design: 7 PM in Sydney is 2 AM in Los Angeles in the southern winter. You will wake early, which is the plan working. The light window on the plan runs through the late afternoon and early evening, from about 4 PM to 7 PM on the 7 hour plan, so stay outside or by a window until bedtime and keep the first hour after waking dim.

Days two and three. Bedtime moves about 1 hour 45 minutes later each night. On the 7 hour plan that is 9 PM on night two and your usual 10:30 PM on night three; on the 5 hour plan you are at 10:30 PM on night two. The plan reaches Sydney time in 5 days from April to October and 4 days from November to March.

Auckland. From November to March the shift is 3 hours, and two prep nights cover two of them: the first night in Auckland is already at your usual 10:30 PM and the plan is done in 3 days. From April to September it is a 5 hour shift with the same 4 day plan as summer Sydney.

If you fly without prep nights, or you are reading this on arrival, switch the calculator to "I already landed". The first sleep window then starts at 5:15 PM Sydney time on the 7 hour plan and 7:15 PM on the 5 hour plan, and the plan reaches local time in 3 to 4 days.

Open the outbound plan for Los Angeles to Sydney or Melbourne, or the Auckland version. Already there? Start from tonight.

Flying home

Sydney to Los Angeles is the same 5 to 7 hours as an advance, and it is the harder leg. The calculator estimates 5 days of recovery from November to March and 7 days from April to October, against 4 to 5 going out. Auckland is 3 to 5 days.

The flight leaves Sydney in the morning and lands in Los Angeles in the morning of the same calendar day, 13 to 14 hours later. You get the lost day back, but you arrive at what your body reads as late evening with a full day ahead, and the first night at home starts late.

The return plan with two prep nights moves bedtime an hour earlier each night before you fly, 9:30 PM then 8:30 PM Sydney time, with bright light after waking and a dim two hours before bed. On the night you land, the sleep window runs from 2 AM to 10 AM Los Angeles time on the 7 hour plan and from midnight to 8 AM on the 5 hour plan. Light in the hour or two after waking does the work from there; the two hours before bed are the avoid-light window. Bedtime then moves about 90 minutes earlier each night, reaching your usual 10:30 PM on night four on the 7 hour plan and night two on the 5 hour plan. The plan reaches Los Angeles time in 6 days from April to October and 4 days from November to March.

Expect the classic advance symptoms: hard to fall asleep, hard to wake, and an afternoon slump around what your body still thinks is 3 AM. Keep any nap under 30 minutes and before 3 PM.

Open the return plan for Sydney or Melbourne to Los Angeles, or the Auckland version.

Short trips

Almost nobody flies to Australia for two nights, but the rule holds if you do: under three nights, stay near Los Angeles time and schedule around it. On a Los Angeles clock, Sydney's early morning is your early afternoon and its evening is your small hours, so the mornings are your productive time and the evenings are for sleep.

For most trips, which run a week or more, adapt on the way out, and treat the last two nights in Australia as prep nights for the return by moving bedtime an hour earlier on each. That turns the 7 hour advance home into a 5 hour one before you board, and it is the single most useful thing on this route.

Where a shorter stay makes adapting pointless, use the "I already landed" plan for the nights you are there and stop when you leave.

Light, melatonin and caffeine

The three levers point in opposite directions on the two legs.

Light. Going out, the clock needs to move later: seek light in the late afternoon and evening, keep the first hour after waking dim, and avoid a bright early-morning start on the first two days. Coming home, it flips: bright light in the hour or two after waking and dim light in the two hours before bed. Australian daylight is strong and mostly outdoors-friendly, so the outbound plan is easy to follow; the return plan needs a morning walk in Los Angeles more than anything else.

Melatonin. The Cochrane review by Herxheimer and Petrie found the clearest benefit on eastward trips of five or more time zones, with melatonin taken close to the target bedtime at the destination. On this route that is the return leg, and only in the 5 or more hour season. For westward travel the evidence is weaker but still favourable for sleep onset, with the westward studies taking it shortly before the desired sleep time. The doses studied ran from 0.5 to 5 mg, with the low end doing as well as the high. Whether any of that suits you is a question for your doctor or pharmacist. The Melatonin Timing Calculator shows the timing the studies used for each direction.

Caffeine. The outbound trap is coffee on the arrival morning turning into coffee all day. With a 7:15 PM first-night bedtime, the Caffeine Cutoff Calculator puts the last coffee at about 10:45 AM Sydney time; on the 5 hour plan with a 9:15 PM bedtime it is about 12:45 PM. Coming home, a 2 AM first night gives a cutoff around 5:30 PM and midnight gives 3:30 PM, moving earlier each night as the plan advances. The lost night on the flight out leaves a debt whichever way you cut it; the Sleep Debt Calculator will show it is cleared faster by the plan's early bedtimes than by a long lie-in on day two.

Educational information, not medical advice. Consult a healthcare provider for sleep disorders or before taking any supplement.