Formal & Literary: This is a formal idiom (chengyu). It's most common in writing, speeches, news reports, and song lyrics. It adds a touch of elegance and gravity.
Describing Young Elites: It's frequently used to describe groups of outstanding university students, young entrepreneurs, innovative scientists, or artists who are making a name for themselves.
Nostalgia: People often use it to look back on their own past. An older person might say, “想当年我们也是风华正茂的” (Xiǎng dāngnián wǒmen yěshì fēnghuá zhèngmào de), meaning “Back in the day, we too were in our glorious prime.”
Social Media: While formal, it can appear on social media, often with a touch of sentimentality. For example, it might be used as a caption for graduation photos or a post celebrating a young person's achievements.
Connotation: It is always positive, complimentary, and uplifting.