According to the March 2016 issue of Empire Magazine Wonder Woman is over 5000 years old. According to actress Gal Gadot (who portrays Wonder Woman) this un-agingness forms a key part of her back story and explains her absence for the past hundred years, that 'man's inhumanity to man' and more specifically the sight of mechanised warfare have emotionally overwhelmed her, to the point that she simply withdrew from the superhero biz for a few generations.
Using Greek mythology as the backbone to her backstory, she was born
Princess Diana of Themyscira, an Amazonian warrior with superhuman
strength and athleticism, and a golden lasso. In some comic-book
strands she is the daughter of Zeus.How all this will be recalibrated
for the realitydetermined context set up in Man Of Steel remains
elusive, though Gadot confirms that when it comes to inborn talent,
her metahuman heals quickly, jumps to heights where she is almost
flying and can really pack a punch.
She is also over 5,000 years old.
“Because she’s seen it all,” says Gadot, “she has seen what humans can
do, so it was very hard for her to come back and fight.”
Empire Online - Gal Gadot