This past Sunday’s episode saw our heroes facing off against an undead polar bear, the night king, and a whole army of his undead infantry. Their quest to capture a wight eventually leaves them stranded in the middle of a frozen lake waiting for Daenerys to (hopefully) come save them. This is where the timeline begins to get sticky because it appears that it only takes around 24 hours for Gendry to run back to Eastwatch, send a raven to Dragonstone, and Daenerys to fly back and save the day.
Based off what Jon said to Sansa earlier in the season, it would seem that the two locations must be 1,000+ miles apart; while it may be conceivable that a dragon could fly that far in such a short period of time, a raven doing so seems ridiculous—even for a season which is already blurring timelines more than ever before in the show.
The director of the episode, Alan Taylor, addressed the problem in an interview earlier this week:
“In terms of the emotional experience, [Jon and company] sort of spent one dark night on the island. In terms of storytelling moments we tried to hedge it a little bit with the eternal twilight up there north of The Wall.”
According to Taylor, the region north of the wall is akin to the North Pole as far as solar and lunar patterns are concerned. This is actually a familiar concept in the show, as winter is repeatedly referred to as “the long night”—a familiar concept to anyone who has experienced a winter in the far north. Perhaps this long night refers to an abnormally prolonged state of twilight and as winter progresses the nights become longer and longer until the whole north is covered in twilight—sometimes for years at a time.
Either way, everyone on the show seems to agree that the Starks were right all along and winter is here—albeit it in its beginning stages. In context, it seems fairly plausible to think that John and his company could have spent much more than 24 hours stranded on that island despite only experiencing one sunset/sunrise.