Bug on the update date

Good morning,
I need to display the update date in the snippet of google.
In the function.php of my child theme, I put the function to display all the data in Hatom.
I do a structurated data test and I see this:

hatom
0 ERRORI
0 AVVISI
expand_less
@type
hatom
hentry
@type
hentry
bookmark
http://www.fisioterapiarubiera.com/testicolo/problemi-di-erezione/
entry-title
Problemi di erezione
updated
19 maggio 2014

But the updated date is 4 may 2018.

Why it doesn’t give me the correct update date?

Many thanks

The page I need help with: [log in to see the link]