yes the grand slam only counts if started from January too .Thats why its 3 times tougher to achieve mathematically
Never understand the importance of results occurring within a calendar year in tennis when it is pretty much a continually-going sport.
It's three times harder to win 4 slams in a row starting from the French Open as well. Yet we label the one starting from AO as somehow more valuable than one starting from any other slam.
If one player wins 4 GS in his career from 2013 AO - 2013 USO, and another player in an alternate history won 4 GS in his career from 2013 FO - 2014 AO, if all their other achievements were identical, it boggles my mind as to why some people would consider the first player a greater player than the second.