Seniors tax implications on a quit claim deed

Hello,

 

I bought a property back in 2007 been living with my parents but then I moved out of the house back in 2015. 
I did a quit claim back in December 2021 and transferred the house to my parents.
 
My question now is that, my parents are now both 67-68 and still working making 85K a year on top of their monthly pension. If they sell the house they are going to have at least 400K in gains.  I am no longer in the (2 years within the last 5 years) range when I did the quit claim, so I am wondering if this gain is a long term gain or short term gain or how would tax implications going to affect them.
 
Thank you!