Songfacts®:

• Here, Julia Michaels links up with Niall Horan to mourn the end of a relationship. During the sweetly nostalgic song, they recall the ups and downs of the romance. Though it didn't end well, they are able to look back fondly and remember "what a time" they had together.
• Michaels and Horan first got to know each other when she opened for the former One Direction singer during the European leg of his Flicker World Tour in early spring 2018. She told Billboard Horan is very easy to work with, and produces the goods too. "We always make fun of each other for a second, then he sings his heart out, and then he's like, 'Cool, I'll see you later,'" Michaels said. "And all of a sudden there's this magical vocal on this song, and he sounds like a sweet baby angel."
• Julia Michaels wrote the slow pop song with her frequent songwriting partner Justin Tranter (Selena Gomez' "Good For You," Justin Bieber's "Sorry" and Hailee Steinfeld's "Love Myself").
• The producers are:
  
  Julia Michaels' longtime collaborator Ian Kirkpatrick (Selena Gomez' "Bad Liar" and "Look at Her Now").
  
  Casey Barth and Riley Knapp, who comprise the Los Angeles' electro/R&B duo RKCB. They also worked with Michaels on her "Happier" track.
• Michaels first performed "What A Time" solo when she opened for Maroon 5 on their 2018 Red Pill Blues Tour. After recording it as a duet with Horan, the pair performed the song together for the first time on the February 18, 2019 episode of The Late Late Show with James Corden. She released it as her second single from Inner Monologue Part 1 on March 29, 2019.
• Boni Mata directed the video, which features Michaels and a Horan look-alike sitting back-to-back in an apartment overgrown with flowers. Michaels grows more emotional as she reminisces about their past love, but the man remains unmoved.
• The song entered the UK chart for the first time in May 2021 after it went viral on TikTok.