in somebody's day

Từ điển Oxford Advanced Learner 8th

in sb's ˈday idiom
1. during the part of sb's life when they were most successful, famous, etc
•She was a great dancer in her day.
2. when sb was young
•In my day, there were plenty of jobs when you left school.
•In Grandfather's day, owning a television was very unusual.
Main entry: ↑day_idiom