So you've exhausted all your options - melatonin, prescription sleeping pills, alternative therapies such as lavender oil, changed your eating times and got some exercise - and still can't seem to beat jet lag? Next time, try some good old mathematics for a change. Researchers at the University of Michigan have created a free iPhone app that offers users lighting schedules that they say are mathematically proven to adjust you to new time zones as quickly as possible. The app Entrain was launched this month, and is believed to be the first to take a numbers-based approach to "entrainment" - the scientific term defined as "alignment of an organism's circadian rhythm to that of an external rhythm in its environment". "Overcoming jet lag is fundamentally a math problem and we've calculated the optimal way of doing it," says Danny Forger, a professor of mathematics at the university's College of Literature, Science, and the Arts. "We're certainly not the first people to offer advice about this, but our predictions show the best and quickest ways to adjust across time zones." The foundation of the app is two sets of equations devised by Forger and colleagues in the '90s that have been shown to accurately describe human circadian rhythms, or the body's biological clock. The clock is regulated by light, particularly from the sun and in wavelengths that appear to our eyes as the colour blue. The researchers used the equations and a technique called optimal control theory to calculate ideal adjustment schedules of light and darkness for more than 1,000 possible trips. A detailed explanation of the math is published in a study in PLoS Computational Biology . Simply put, by exposing yourself to light at the right times, the body's clock can be more quickly and efficiently steered to a new time zone. Sometimes, the app will request darkness when your own schedule requires light. You can try blocking the light with orange-tinted glasses to approximate darkness, say the researchers, or using a 10,000 lux lamp inside to simulate full daylight. If you're travelling home from Doha to Hong Kong - five hours ahead - the app can adjust you in about three days. If you veer from the schedule, update your lighting history in the app and it will recalculate going forward, lengthening the adjustment period. The metrics page in the app plots two curves - one for your body clock and another for the goal rhythm - a visual guide to how the lighting will help you adjust to the new time zone. The curves will begin to line up as you adjust to your new schedule. Unfortunately, my attempt at using the app failed miserably. It was hard to figure out what I had to input and also difficult to make sense of the schedule. It all seemed a little technical and lacking in the human touch. A how-to guide would have been useful, as well as a friendlier interface. Maybe you'll have better luck with it: check out the app at www.entrain.org or download it from the App Store. Users may opt-in to submit their data to the University of Michigan anonymously. The researchers say the data submitted will be used to help test and improve the recommended schedules. One goal of the iPhone release, they add, is to get user feedback to improve the app so that the future Android release runs smoothly.