That sound you hear is yourself throwing every thought you had in your brain about buying plane tickets on a certain day out the window. As the window shatters, so can your mind break free from former apparent misconceptions regarding the best day to purchase air fares. It’s not the day you thought it was, it’s Sunday.

So say the tallies totted up by Airlines Reporting Corp, according to the Wall Street Journal, a group that processes tickets for traditional travel agencies and online booking (though not direct sales from airlines) and sees about half of all the tickets sold.

After taking a look at ticket sales over a 19-month period ending in July, 130 million domestic and international round-trip fares showed that the lowest average price of $432 was on Sunday. That’s lower than $439 for Saturday ticket sales and Tuesdays, with an average of $497.

What makes Sunday the magic day? It’s the day before airline executives come into work on Monday looking to make more money for their companies, a prime day to raise fares instead of discounting them to fill seats. And raising fares is a thing that can make more money — as reported earlier this week, many airlines pushed through a fare hike recently, despite the fact that fuel prices are down and some travelers may be worried about flying due to the Ebola scare rampaging through the news.

That being said, don’t dump your Tuesday hopes all together: As the WSJ points out, it’s still the day with the most frequent discounts, so you could still score a good deal if you’re paying attention.

The ARC study also showed that the cheapest time to buy a domestic trip is about 57 days before departure, or around two months, which is quite early for most people. On average, travelers book airline tickets about a month beforehand, when prices are already on the uptick.

In conclusion: two months before you go somewhere, check out prices on Sunday, your new best friend of a day.

The Best Day to Buy Airline Tickets [Wall Street Journal]

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