Of advanced years
Definition 1 of 1
Pro Tip 1/3Respectful Term
Used to describe someone older with respect, often used to avoid calling someone old directly. 
My grandfather, a man of advanced years, still enjoys cycling on weekends.
Pro Tip 2/3Positive Connotation
Carries a positive tone that acknowledges experience and wisdom that comes with age. 
The author, of advanced years, shared her invaluable life lessons in the lecture.
Pro Tip 3/3Formal Contexts
Appropriate for formal situations, like in writing or formal speeches, to show politeness and respect. 
The ceremony honored citizens of advanced years for their contributions to the community.