Crossing time zones desynchronises the internal clock from local time, and recovery follows a rate that cannot be rushed much.
The circadian system
An internal rhythm entrained mainly by light.
Which shifts by roughly an hour a day.
Direction asymmetry
Eastward travel generally harder than westward.
Which reflects the clock running slightly longer than a day.
Light timing
Exposure at the right time accelerating adjustment.
Which is the main lever available.
What does not help much
Most of the folk remedies, which have little supporting evidence.
Why light timing is the whole strategy
The internal clock is set primarily by light reaching the eyes, and exposure at the wrong time shifts it in the wrong direction.
Which means seeking light in the destination morning after eastward travel and in the destination evening after westward travel is the intervention with the clearest evidence.
Getting this backwards, which is easy when arriving exhausted, actively delays adjustment, and it is the most common avoidable error.
Rate of adjustment
Roughly an hour a day, faster westward.
Which sets a floor on recovery time.
Short trips
Sometimes better not to adjust at all.
Which suits trips of two or three days.
Sleep aids and melatonin
Evidence varying and timing mattering more than dose.
A general note
Anyone with a medical condition should take advice before using sleep medication.
What actually makes a trip go well
Very little of it is the things travel content concentrates on. It is not the property, the itinerary or the equipment. It is preparation on a small number of specific points, a pace that leaves room for things to go wrong, and enough humility to ask people who live there.
The trips that go badly are usually the ones where something checkable was not checked: an entry requirement, a health preparation, a transport connection, or the assumption that a place would be like somewhere else. All of those are answerable in advance and none of them takes long.
The preparation that repays itself
Entry requirements from the destination’s own authority. Travel health advice with enough lead time for vaccinations. A realistic daily budget including local transport, food and activities. Twenty words of the language. Somebody at home who knows roughly where you are.
That is an hour or two spread over the weeks before departure, and between them those five things prevent most of the situations that turn an ordinary problem into a serious one.
The travel that seems to be worth most
Longer stays in fewer places, some contact with people who live there rather than only with people paid to serve you, and a willingness to be uncomfortable occasionally. That is what the research on attitude change points at, and it is also what people describe when they talk about trips that mattered to them.
None of it requires money. Some of the most valuable travel is the cheapest, which is not what the industry has an interest in saying.
A general note
Entry requirements, health advice, safety conditions and local law differ enormously by destination and by nationality, and they change. Official sources for your own nationality and your specific destination are the only reliable reference, and nothing here is a substitute for checking them.
What travel writing tends to leave out
Most of it is written to inspire rather than to inform, which means it emphasises the extraordinary and skips the logistics. That is a reasonable commercial choice and it produces a systematic gap: the things that actually determine whether a trip works are rarely the things that get written about.
Entry requirements, health preparation, realistic budgeting, transport connections and what a place is actually like to be in on an ordinary Tuesday are all considerably more consequential than any recommendation, and considerably less photogenic.
On the destinations themselves
Almost every place is more ordinary and more interesting than its reputation. The reputation is built from a handful of images that a great many people have now seen, and arriving expecting them produces disappointment that has nothing to do with the place.
The parts of a destination that people remember afterwards are generally not the ones they went for, which is an argument for leaving room in an itinerary rather than filling it.
Where to get reliable information
Foreign ministries publish entry requirements and safety advice for their own nationals. Travel health services publish destination-specific medical guidance. National tourist boards publish practical information without a commercial interest in any particular property.
All three are free, current and specific to where you are actually going, which is more than can be said for most of what a search returns.
One habit worth adopting
Ask someone who lives there. Accommodation staff, drivers, shopkeepers and people at the next table know things no guide contains, and most of them are pleased to be asked.
It is also the part of travelling that people remember, which is a reasonable argument for it beyond the practical one.