There are various synonyms for the phrase "best days," some of which include golden years, heyday, prime, pinnacle, peak, zenith, apex, crowning moments, high points, and halcyon days. These words depict a span or period in someone's life that was filled with joy, accomplishments, and happiness. It could be a time when everything seemed to align perfectly, and one felt content and fulfilled. The synonyms for "best days" allude to a moment in life that one wishes to revisit, and can be used interchangeably to represent the glory days of one's life when everything was just right.