Jehovah's Witnesses' three periods

Among modern formations of religion, arisen within Christendom, there is no one that has changed its doctrine and attitude so much as Jehovah's Witnesses, so that the religious content in the three periods can be labelled as new, newer, the newest. Each period is connected with and dependent upon the three presidents Charles Taze Russel, born in 1852, president 1881-1916, Joseph Franklin Rutherford, born in 1869, president 1916-1942, and Nathan Homer Knorr, born in 1905, president from 1942. The purpose here is to clarify some important differences between the three periods.