Novak Djokovic set a new landmark of 311 weeks as world number one on Monday, one week longer than Roger Federer whose tally of a record 20 Grand Slam titles is now firmly in the Serb’s sights, reports AFP. Djokovic, 33, won his 18th major at the Australian Open in February. With Federer turning 40 in August, the Serb has time on his side. He is also a year younger than Rafael Nadal who also has 20 majors. "It really excites me to walk the path of legends and giants of this sport," said Djokovic, in a statement released by the ATP.