Flying London (LHR) to Sydney (SYD) shifts your body clock 9 hours eastward, which typically means about 9 days to adjust — severe jet lag.
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Build my LHR → SYD planEach recommendation below is graded by how strongly published research supports it, with the source it comes from. Optimal timing depends on your travel direction, the number of time zones crossed and your own circadian phase, so treat the schedule as a starting point.
Bright light after your destination wake time helps advance your body clock when travelling east.
CDC Yellow Book 2026Light at the wrong hour can push your clock the opposite way, so dim screens and lights before your target bedtime.
NIH — Circadian rhythmsMoving sleep and wake times 30-60 minutes earlier for a few nights gives your clock a head start on an eastward trip.
CDC Yellow Book 2026Sleeping, eating and being active on local time gives your body consistent cues about the new day.
CDC Yellow Book 2026Low-dose melatonin near the local bedtime can help with sleep timing after crossing several zones; timing matters more than dose.
Cochrane review — Melatonin for jet lagCaffeine can help you stay awake during local daytime, but late doses tend to delay sleep onset.
CDC Yellow Book 2026Arriving without a large sleep debt makes the first days easier, even when few time zones are involved.
CDC Yellow Book 2026This is general travel information, not medical advice. Talk to a clinician before using melatonin or sleep medication, especially if you are pregnant, take other medication or have a sleep disorder.
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