Made up holidays are getting a little much. Did you know Sunday was National Potato Day? Or that next Thursday is National Trail Mix Day? But here’s one worth paying attention to: In addition to being National Sponge Cake Day, today, August 23rd, is also National Cheap Flight Day. So in addition to eating your body weight in Genoise, you can also book a cheap flight to Italy and eat it like a local.

National Cheap Flight Day isn’t just some arbitrary date picked to boost sales of potatoes or trail mix. Today marks the beginning of the two-week period where airfares historically drop after the rush of summer, and before they start to creep back up in advance of the holidays.

“From today on, there’s about a three-to-four week window where you’ll see some very aggressive pricing,” said Tom Spagnola, senior vice president of supplier relations at CheapOair, who’s researched loads of historic pricing data. “There’s a lull for September and early October, and we’ll see some great pricing both in the US and in international markets during their slow season.”

“There’ll be discount pricing (for flights) through around March of 2019,” he added. “So there’s about a five month window with exceptional prices.”

That means if you’re thinking about a New Year’s trip, a Valentine’s Day getaway, or even spring break, you might want to start planning it in the next few weeks. Because airfares won’t be getting any lower the rest of the year.

If you’re looking to book holiday travel, this is the best time to knock that off your to-do list as well. Skyscanner, the app that tracks airline pricing with disturbingly thorough research, found that the week of August 27th saw seven percent cheaper flights over Thanksgiving weekend compared to the rest of the year. The next best week is October 1st, with six percent savings.

For its part, CheapOair is celebrating the beginning of low fare season with a one-day sale on August 23rd, when Spagnola claims his site will have a number of “double digit discounts,” including some big international flights discounted 20 percent.

“The Asia market has gotten so big and has so much capacity, it won’t be unusual to find fares from the West or East Coast for $500 total,” he said.

If you’re looking to go to Europe, SAS is having a monster sale from now until August 30th, when flights to Denmark, Sweden, Norway, and Finland will be as low as $449. That’ll be good for travel between November 1st and June 30th, so this might be the year you finally see the Northern Lights.

Is any of this an exact science? No more than National Linguini Day (September 15th!) is a federally recognized holiday. But if history holds true the next few weeks will be your best chance of the year to score some cheap airfare. And maybe instead of celebrating National Bologna Day this October 24th by stuffing your face with Oscar Meyer, you can spend it in actual Bologna.