The turn of the century/year
Definition 1 of 2
Pro Tip 1/3Historical Moments
Used to emphasize significant historical events around a new century/year. 
At the turn of the century, many innovations emerged that changed daily life.
Pro Tip 2/3Cultural Shifts
Highlights cultural or societal changes associated with a century's start. 
Fashion radically changed around the turn of the 20th century.
Pro Tip 3/3Figurative Use
Sometimes used metaphorically to express change or new beginnings. 
Joining the new company felt like the turn of the year for her career.