Grand Slam is a general sports term applied when achieving something special.
Most common uses:
In tennis, winning the Grand Slam is winning the following four tournaments in the same year: Australian Open, French Open, Wimbledon, US Open. Those tournaments are therefore also known as the Grand Slam tournaments.
... 21 - Robert Montgomery, actor (+ 1981)
June 2 - Johnny Weissmuller, American swimmer and actor
July 12 - Deng Xiaoping, Chinese politician and leader
July 13 - ...