/ˈheɪdeɪ/
hey·day
BrE /ˈheɪdeɪ/
NAmE /ˈheɪdeɪ/
[usually singular]
the time when sb/sth had most power or success, or was most popular
SYN prime
In its heyday, the company ran trains every fifteen minutes.
a fine example from the heyday of Italian cinema
a picture of Brigitte Bardot in her heyday