If you are wondering when exactly did NewJeans debut and with what music, here is the full answer with the date and first song & MV.
NewJeans Becomes 1st K-pop Girl Group to Achieve THIS on Spotify
NewJeans Day, NewJeans Wiki
NewJeans - The 1st EP: New Jeans (Member Debut Profile Photos / Videos) : r/kpop
LEAD) Rookie girl group NewJeans makes impressive debut on charts
Newjeans - Newjeans 1st Ep 'new Jeans' (cd) : Target
NewJeans: A Spectacular Debut Year and Record-breaking Triumphs in the Kpop World
K-Pop Girl Group NewJeans Makes Official Debut
How K-pop group NewJeans became an overnight fashion favorite
NewJeans Members Profile and Facts (Updated!) - Kpop Profiles
NewJeans Debut Photos