“How many hours ahead is that, again?” somebody asked.

“Six. Amsterdam is six hours ahead of New York.” I already felt bleary-eyed just from saying it out loud. It’d always been easier for me, the unrepentant night owl, to head east than west without feeling like total garbage.

But this trip was different. I’d be there for 10 days, and I didn’t want to sleep until noon, as on past trips. I wanted to see Amsterdam in the morning light. Nevermind that I rarely saw New York in the morning light, and all I had to do for that was go outside.

But somebody had recommended an app called Timeshifter, designed to help you gradually shift your sleep patterns so that when you arrived in another part of the world, you’d be adjusted to the local time and free of jet lag. Besides, there was a free trial, so what did I have to lose?

How Does Timeshifter work?

Your body works according to its own internal clock, something called a circadian rhythm, influenced by your sleep patterns and exposure to natural light. Normally, it finds its own equilibrium with our local clocks, but when you abruptly find yourself in a new time zone, your circadian rhythm is all out of whack.

It takes a while to adjust gradually over the next few days. Larger differences in time take longer. In the meantime, this jet lag can make you feel nauseous and overly tired. It’s not fun, and it can put a damper on a vacation.

Timeshifter works by taking all the work out of determining how you should adjust your sleep schedule in the days leading up to your trip. You input your flight details, including your departure date, starting location, and destination. Then you put in when you normally go to bed, and for how long you typically sleep each night.

The app then comes up with a schedule that tells you that X number of days before you leave, you should go to bed at Y time. Then the next day, a little earlier. And so on. It builds out an entire sleep schedule for you to follow so that your body’s circadian rhythm begins adjusting before you even arrive at the airport. When you land in your destination, jet lag is minimized because you’re already adjusted to the time difference.

Did it work? It didn’t set off any gigantic light bulb moments for me, but then again, I was waking up a decent-for-me time of 9 a.m. local time in Amsterdam, something I’d never done on past trips. No nausea, no fatigue, and no uptake in the amount of caffeine I drank each day. It just took about a week of slowly shifting my bedtime earlier and earlier each day before I left New York.

Unlike a lot of free trials for, well, everything, Timeshifter doesn’t limit you to a particular length of time before it sticks its hand out and demands pay. You get one trip to try it out. That’s a split blessing. You get one complete trip out of it, so you get the app’s full effect for the duration, not some abbreviated version.

But then you only get the one trip. If you want to see how well it does at helping you adjust when you’re making the return journey on your trip back home, you’ll have to fork over either $10 per trip or $25 for an unlimited number of trips for a year.