The major clue you might have missed in new Game of Thrones trailer

The latest Game of Thrones teaser finally revealed when the show will return. Photo / HBO

Bust out the calendar and start scheduling your Sundays accordingly, because HBO has finally revealed when "Game of Thrones" will return: April 15.

That very practical tidbit of information comes at the end of HBO's latest teaser for the show's eighth and final season, which will last six, long episodes. Unlike previous Season 8 teasers, this one isn't just a mash-up of previous episodes, and it contains some very useful reminders regarding lineage.

Published Monday, the teaser features Jon Snow, Sansa Stark and Arya Stark touring the crypt under Winterfell, where statutes of their ancestors and recently fallen stand. We hear voice-overs of now-dead Starks from previous seasons: Lyanna Stark saying, "You have to protect him;" Catelyn Stark saying, "All this horror that has come to my family, it's all because I couldn't love a motherless child;" and Ned Stark saying, "You are a Stark. You might not have my name, but you have my blood." A feather falls to the ground.

Then the three living people come face-to-face with statutes of themselves as they look now, which is generally freaky and also pretty scary given the implication! A gust of wind extinguishes their torches, the cold takes over and ice creeps toward them, freezing everything in its path, including the feather. Arya and Jon draw their swords as they confront whatever kind of undead situation is before them.

As always, there's a lot to unpack in Game of Thrones' latest trailer. Photo / HBO

Now, this teaser is probably just that - a snippet of a scene that won't be in an actual episode but focuses on some essential themes ahead of the new season. So let's unpack it all, shall we?

Firstly, remember: Jon Snow is the child of Lyanna Stark and Rhaegar Targaryen, a fact Jon doesn't know yet (you know nothing Jon Snow, etc. etc.). The Lyanna voice-over ("you have to protect him") was her exhortation to her brother, Ned, on her deathbed: She asked a young Ned to protect her newly born baby.

But think further back, to April 2011, when "Game of Thrones" premiered on HBO. The first Obama administration, Prince William marrying Kate Middleton, the Arab Spring - this was a long time ago, so you'd be forgiven for forgetting how this GoT story all began. During the pilot, Robert Baratheon (King Robert) visits the crypts in Winterfell and puts a feather in the hand of the statute of Lyanna, who he was supposed to marry. King Robert tells Ned how he dreams of killing Rhaegar every night; Ned replies, "It's done, your grace. The Targaryens are gone."

"Not all of them," King Robert replies, which is very true, but at the time we were led to believe he was referring to Daenerys and Viserys Targaryen (since that episode cut to them). Now, we all know it also refers to Jon Snow himself.

The next time we see that feather is during Season 5, when Sansa visits the crypts and picks up the feather at the feet of her aunt's statute and puts it back in her hand. She and Littlefinger then review the widely-accepted story about Lyanna and Rhaegar: that he won a tournament but rode past his wife, Elia Martell, and instead chose Lyanna. The way it's been passed down is he kidnapped and raped Lyanna, which led to Robert's Rebellion and Robert Baratheon's installation on the Iron Throne.

The all-important feather from the new trailer. Photo / HBO

But, as finally confirmed in the Season 7 finale, Lyanna and Rhaegar were actually in love and secretly married. (Bran Stark has seen it; speaking of which, why isn't he in the crypt during the teaser? Let's speculate wildly on that one . . .)

This all sets us up for Season 8, which we're lead to believe will finally zero in on Jon's true parentage. We're hoping it doesn't take too long for him to know the truth, which means he'll realize two things: He's actually an heir to the Iron Throne, and he's had sex with his aunt, Daenerys. It ain't "Game of Thrones" without a little incest, after all.

Season eight of the highly anticipated series will screen in New Zealand on SoHo, the same day as it screens in America: 1pm on April 15.