That is, 300, the number of weeks he will have spent at world No. 1 if he beats Stanislas Wawrinka in Shanghai, according to the The Telegraph.
Federer captured the all-time record earlier this year when he surpassed Pete Sampras' 286 weeks. Meanwhile, Federer already had the record for consecutive weeks on top at 237.
Going against compatriot Wawrinka—with whom he earned a gold medal at the 2008 Olympics—Federer has to feel good about his chances.
While Federer received a strange death threat prior to the tournament, it has not had an impact on him on the court so far.
World No. 17 Wawrinka has already matched his career best at the Shanghai Masters by reaching the third round. The last time Federer played in Shanghai in 2010, he reached the final, but lost to Andy Murray.
When asked about the 300-week mark, Federer simply said (via The Telegraph): "It’s a big number."
The fact is, it's been a resurgent year for the 31-year-old. Federer won Wimbledon, the World Tour Finals and four Masters tournaments.
If he can secure the No. 1 rank at the end of the year, which he is on a good pace to do, he will secure at least 315 weeks at the top and greatly extend his lead over Pete Sampras, Ivan Lendl and other former greats.
The biggest road block to finishing the year at No. 1 for the sixth time in his career will be the World Tour Finals. He stands to lose up to 1500 points at that tournament, which could potentially open the door for world No. 2 Novak Djokovic.
In the meantime, Thursday will most likely see Federer locking up another milestone achievement that might stand the test of time.