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.
Said when one is looking back on something enjoyable or worthwhile in the moment that it was happening even though it was impermanent
The party came to an end, but it was fun while it lasted.