Granted the margin of error of this guestimation, not all countries have censuses and even many that do are not high quality, is plus or minus six months so who knows when and where the seventh billion human alive was born.
While this growth seems fast most population estimates have the world's growth slowing down. According to most demographers, the world's population will reach 9 billion around 2050 and stabilize.
To celebrate seven billion humans the BBC has made a web application that allows one to see where they are in the world's population count based on birthday. Comparing the my ranking to that of my parents and grandparents current showed the quick rise in the world's population.