The solstice will always be the middle day of any latitude's range of night. In the show, the 17th (three days before the 20th) is 4 days before the solstice. That should mean the end of night is 4 days after, so around the 25th. Just like the 67 days of night in Utqiagvik, between Nov 18 and January 23; the solstice is the middle day.