Airline ticket buying advice is mostly all stupid. That is except, of course, mine.
I’ve heard countless theories about when the best time to buy a plane ticket is. You can buy it on a Tuesday or Wednesday, three months or exactly 183 days out from departure, or even better, when a black cat decides to cross a ladder. I've always called it a voodoo science for a reason. The truth is, at the end of the day, there really is no substitution for advance planning.
Just to illustrate how bogus airline buying advice can get, Gary Leff from View from the Wing held a pretty silly contest about anyone who could concoct the most ridiculous-but-possibly-true hypothesis on why it’s best to book a ticket in the wee early hours of Friday. Larry V ended up posting this awesome theory that sounds just as good as anything that's published these days:
3:15am on a Friday is the best time to book a ticket (note: This is 3:15am UTC, or Universal Coordinated Time). Why? Because this corresponds to 5:15pm at the International Dateline (UTC+14).
Back when the airlines were designing more sophisticated revenue management computer algorithms in the 80s, they knew that businesses were most likely to pay higher fares, so they designed a “5 day business day window” which corresponded to the typical 9-5 business week. They designed them to load the highest fares at 9am on Monday and ended them at 5pm on a Friday. However, the programmers had to pick a starting point, and so they picked the starting point as the time at the International Date Line, so that the very first cities to experience the new business day would start buying the new fares.
At 5pm on Friday at the International Date Line, these 5-day window of higher fares expires, and the leisure fares are reloaded. It takes time to propagate through the system, so 5:15pm (or 3:15am UTC) is a good guideline to make sure all the business fares have expired.
It is of course true, because everything on the Internet is. You decide.