In your eighties
Definition 1 of 1
Pro Tip 1/3Age Range
Specifies someone's age without giving the exact number, suggesting advanced years with a degree of vagueness. 
The author, in his eighties, released his final novel.
Pro Tip 2/3Admiration Tone
Expresses respect or admiration when someone in their eighties maintains certain abilities or activities. 
He's in his eighties and still runs marathons!
Pro Tip 3/3Not Precise
Avoid using it when precise age is important, as it covers a ten-year span. 
During the census, you'll need to provide your exact age, not just 'in your eighties'.