You might need to set an alarm. 

The next great adventure is on the horizon. But with ever-fluctuating airfares, it's not always easy to secure an ideal rate. According to the travel fare website Skyscanner, here are the best times to book your next flight.

Put your planning prowess to good use and prepare to book in advance! Allow two to three weeks before your departure date to score reasonable rates on a domestic flight. Leaving the country? Start shopping around two months in advance.

It also wouldn't hurt to schedule your trip during an off-season month. If you're looking to snag an excellent deal, plan to travel in January, February, August, or September. Your chance at savings may be higher.

And when you finally have that date set in stone and you're primed to make your reservation, keep one particular day in mind: Sunday. The last day of the weekend is reportedly the best day to book. So have your credit card on standby! But if Sundays prove to be difficult, all other days work as well—as long as you keep an eye on the clock. Skyscanner says that 5 a.m. is truly the best time of any day to land a great deal.

So if you're hoping to spend more on souvenirs, don't forget to set an alarm!