I went back to 1993 (counting Eagles playoff seasons as the year of the super bowl rather than the regular season). It has only happened twice in the same calendar year in that time. 2011 and 2009.
Three teams have made the playoffs 7 times, 2001, 2002, 2003, 2005, 2008, 2010 and 2018 so far. The Phillies were the team to miss out in every one of those seasons except 2008 and 2010. The Sixers missed out in 2008, Eagles in 2010.
There have been four seasons when none of the four made the post season. 1994, 2013, 2015 and 2017.
Between 2015 and 2017 only the Flyers in 2016 made the playoffs. Between 2013 and 20017 you only add to more post season appearances when the Flyers and Eagles made the playoffs in 2014.
Over that 26 (25 and 3/4s for Phillies) season period The Flyers have made the playoffs 20 times. The last time they missed the playoffs in back to back seasons was 1993/94. The Eagles have made the playoffs 14 times, missing between 2015 and 2017. The Sixers have made the playoffs 11 times, missing for five straight seasons between 2013 and 2017 (Trust the Process). Our Phillies have made the playoffs 6 times.... missing out for the last 6 seasons and for 13 straight years between 1994 and 2006.
I know none of this is news but its crazy how quickly the turn around appears to have happened in Philadelphia sports. From 0 teams to potentially 4, and 3 of the four are considered to be real title contenders going forward. I don't pay too much attention to Hockey so I'm not sure where they sit in terms of the future. Are they in a similar position to where the Sixers were back in 2012, consistently reaching the playoffs but doing very little once they get there? They have been in the playoffs 20 times but only reaching the finals twice in that time? Sorry to take this off topic!