The year he turned 17, he won the Budapest Challenger in May and moved into the top 500. The year he turned 18, he qualified for Roland Garros and won his first main-draw match at a major. The year he turned 19, he reached the Roland Garros quarterfinals as the world No. 63 and won his second ATP title in Metz in October. The year he turned 20, he won the Miami Open in April, beat Nadal and Federer to win the Rogers Cup in August, and lost to Federer in his first Grand Slam final, at the US Open in September.
The breakthrough yearThe year he turned 21, he beat Jo-Wilfried Tsonga in the Australian Open final on January 27, and became the first Serb to win a Grand Slam singles title.
The year he turned 24, he beat Nadal in the Wimbledon final for his first title there and became world No. 1 the next day. The year he turned 25, he beat Nadal in a record five hours and 53 minutes to win the Australian Open, and beat Federer in the ATP World Tour Finals in November. The year he turned 26, he beat Nadal in the final of the ATP World Tour Finals in London. The year he turned 27, he beat Federer in five sets in the Wimbledon final and returned to No. 1. The year he turned 28, he beat Federer in the US Open final for his 10th Grand Slam title, the third major of his year. The year he turned 29, he beat Andy Murray in the Roland Garros final on June 5, completing the career Grand Slam and holding all four major titles at once.
The year he turned 30, he announced in July that he would miss the rest of the season with an elbow injury. The year he turned 31, he won Wimbledon as the 12th seed, ranked 21st, and in August won Cincinnati to complete all nine Masters 1000 titles. The year he turned 32, he beat Nadal in the Australian Open final for a record seventh title there. The year he turned 33, he beat Dominic Thiem in the Australian Open final for an eighth title there and his 17th Grand Slam.
The year he turned 34, he equaled Federer’s record of 310 weeks at No. 1 in March, then won Roland Garros in June and Wimbledon in July to reach 20 Grand Slam titles. The year he turned 35, he left Australia on January 16 after the federal court upheld the cancellation of his visa, and missed the Australian Open. The year he turned 36, he won the Australian Open, Roland Garros and the US Open, reaching 24 Grand Slam titles.
The year he turned 37, he beat Carlos Alcaraz in the Olympic final in Paris on August 4 for his first Olympic gold medal. The year he turned 38, he lost to Jannik Sinner in the Wimbledon semifinal in July and won his 101st career title in Athens in November.
The year he turned 39, he beat Felix Auger-Aliassime in a five-set Wimbledon quarterfinal in July, lost in the first round of the US Open in August, and prepared to return at the China Open in late September.
Novak Djokovic (born May 22, 1987) won the Budapest Challenger in 2004, the year he turned 17. He became known in 2008, the year he turned 21, when he won the Australian Open on Jan 27, 2008. He became world No. 1 in 2011 and won his 24th Grand Slam title on Sep 10, 2023.
Ages are by calendar year (the year minus the birth year), birthdays aside.