new century
Refers to a new century, often used in contexts like the start of the 21st century or futuristic themes.
An event was held to celebrate the dawn of the new century.
This movie is set in Tokyo of the new century.
新世紀 narrowly means 'new century', whereas 新時代 is broader and can describe any newly-arrived age or period, not just a 100-year span.
millennials; millennial generation
Compound of 新 (shin, 'new') and 世紀 (seiki, 'century').