Be (on) the wrong side of (an age) informal
Look older than a certain age
Though she is trying to dress young, she's still on the wrong side of 40.
My friend and I are the same age, but she's on the wrong side of 50.
To be in a poor condition.
To be extremely old (a joke or a story)
Used to indicate that the age at which a person's consent to sexual relations is legitimate.
Be nearly a particular age
The verb "be" should be conjugated according to its tense.