When the Television Academy announces its Emmy nominations Thursday morning, several notable names will be missing from the list.

In some cases, the omissions will be self-explanatory. Game of Thrones may be the reigning champ of the Best Drama Series category, but it didn’t air a new season during the 2017 Emmys’ eligibility period, which ran from June 1, 2016, to May 31, 2017. (The last few episodes of the show’s sixth season, which aired in June 2016, were wrapped into its eligibility for the 2016 Emmys — and, indeed, it won writing and directing Emmys for one of them.)

But one name whose absence might provoke alarm is that of Showtime’s Twin Peaks revival, which will not be nominated in any categories. And the reason is simple: Though it aired four episodes before the May 31, 2017 eligibility cutoff, the majority of its 18 episodes will air during the next Emmy eligibility period, which runs from June 1, 2017, to May 31, 2018.

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In general, shows must air half their episodes within the Emmy eligibility period for their seasons to “count.” Any episodes that spill over — in either direction — are nominated alongside their seasons as a whole. So even though the Twin Peaks premiere aired in May 2017, it won’t be eligible for the Emmys until next year, because Showtime will be forced to submit the entirety of Twin Peaks to the 2018 Emmys. (The miniseries is 18 episodes, with only four airing before May 31.)

Ultimately, this eligibility wrinkle will probably help the show’s chances, as it seems to garner more buzz with every week it’s on the air. But it can still be a touch confusing, even for even diehard TV fans.

(Another example: Orange Is the New Black’s fifth season, which launched in the first half of June and already feels like old news as I’m writing this, won’t be eligible for the Emmys until 2018; any nominations the show receives this week will be for season four, which debuted on June 17, 2016.)

The logic behind the Emmys’ “half” rule has developed slowly over time, but they’re rooted in a past Emmy darling: The Sopranos. The HBO drama, which ran from 1999 to 2007, would frequently air its seasons from March to May, but skip Memorial Day weekend. The result was often that one episode, the season finale, would air in June. The Emmy rules at the time prevented that “remainder” episode from being eligible at all — even in the following year — so several memorable Sopranos finales simply didn’t qualify for Emmy awards.

As this scenario befell more and more cable dramas — which were less bound by the “September to May” calendar of the broadcast TV networks — the Emmys eventually, agreed that “rollover” episodes of a show’s season could be applied to the season as a whole. The rules were further adjusted in subsequent years until the Emmys settled on the rule we have now.

However, the most common situation for shows that straddle Emmy eligibility periods is to air a handful of episodes after the May 31 deadline, as Game of Thrones did in 2016. It’s much rarer for a show to air too few episodes during the eligibility period, thus dragging it into a future Emmy window.

So, even though what Twin Peaks is doing isn’t unprecedented, it is unusual. That seems only too fitting for the groundbreaking show.