Using your flight itinerary, two websites will provide suggested sleep schedules based on how many time zones you’ll cross and which direction you’ll be travelling.

While researchers are continuously debating and fine-tuning their advice, they agree that exposure to light is one of the most effective ways to combat jet lag.

“But the rules for when you should seek out or avoid light are complicated and depend on whether you travel east or west and how many time zones you are crossing,” said Russell Foster, head of Oxford University’s Nuffield Laboratory of Ophthalmology and one of the world’s leading experts on jet lag.

Sunlight activates the pineal gland, which triggers a physical process that winds up and sets your body’s internal clock, while darkness encourages your body to sleep by lowering your temperature and sending melatonin, a natural sleep-inducing hormone, into the bloodstream.

But obeying signals from sunlight and darkness – which are key to resetting the body’s internal clock – can be difficult when you’re flying cross-country or halfway across the world. Thankfully, two websites offer step-by-step, personalised help for combating jet lag. Using your flight itinerary, each site provides a suggested sleep schedule based on how many time zones you’ll cross and which direction you’ll be travelling.

Jet Lag Rooster is an online calculator that employs similar guidelines to those used at academic institutions such as the Mayo Center for Sleep Medicine in Minnesota and Rush University Medical Center in Chicago. Type in your itinerary and the site will give you an hour-by-hour breakdown of when to sleep and when to go outside and seek sunlight.

For example, on an Atlanta to Moscow itinerary where a passenger lands at 10 am, Jet Lag Rooster advises a schedule of doing the best you can that first day and night (without specifying particular hours) and then, on the following day, avoid light after 11 am. The next day, it recommends you begin to avoid light a little later – after 12:30 pm – and on the day after that, it suggests you begin to avoid light after 2 pm.

The reasoning behind this advice is that the average person can only adjust their internal clock by an incremental amount of 60 to 90 minutes a day. Jet Lag Rooster encourages travellers to pace themselves accordingly, which means it may take a person travelling between Atlanta and Moscow about seven to 10 days to shift their body clock the necessary 10 hours.

British Airways also created an online jet lag fighting calculator, where the advice is based on research by Chris Idzikowski, director of the sleep assessment and advisory service at Edinburgh Sleep Centre. The science behind the site’s conclusions is the same as Jet Lag Rooster’s, but the tool condenses the advice to a few sentences, rather than give an hour-by-hour breakdown.

It’s important to note that when scientists say you should seek out “light”, they mean ideally being outdoors for up to half an hour. Outdoor light is always better than indoor light. Even an overcast spring day in say, Reykjavik, will provide enough light to reset a body clock, compared with sitting indoors, which won’t. On the flip side, avoiding light can entail wearing sunglasses or staying indoors.

Special light boxes, or flat lamps that simulate natural white light with a blue tint, are also effective, noted Foster, who has been consulting with Delta on the feasibility of introducing such lights into airport lounges. However, there is no word yet from the airline on whether it will put the concept into practice.

Sean O’Neill is the travel tech columnist for BBC Travel