Implantation usually occurs between 8 and 10 days after the egg is fertilized. So if you have a 28-day menstrual cycle and ovulate on the 14th day, implantation would occur somewhere between day 22 and 24 of your cycle. If your cycle is longer, implantation would occur between 2 and 4 days before you would expect your next menstrual period.
Most women do not have any specific symptoms to indicate that implantation has occurred, but a small number of women experience a phenomenon called implantation bleeding around the time of implantation. Implantation bleeding usually involves only very light spotting but occasionally can be confused for a menstrual period because of the timing.
Wilcox, Allen J., Donna Day Baird, and Clarice R. Weinberg. 'Time of Implantation of the Conceptus and Loss of Pregnancy." New England Journal of Medicine 1999. Volume 340:1796-1799.