I have heard around the time of Christ, possibly a bit earlier.
Answer2:SHINTO is predominantly a Japanese religion. According to the Nihon Shukyo Jiten (Encyclopedia of Japanese Religions), "The formation of Shintoism is almost identical with the Japanese ethnic culture, and it is a religious culture that was never practiced apart from this ethnic society." Although Shinto claims a membership of over 91,000,000 in Japan, which amounts to about three quarters of its population, a survey reveals that only 2,000,000 people, or 3 percent of the adult population, really profess to believe in Shinto. However, Sugata Masaaki, a researcher on Shinto, says: "Shinto is so inextricably woven into the fabric of Japanese daily life that people are barely aware of its existence. To the Japanese it is less a religion than an unobtrusive environmental fixture, like the air they breathe." Even those who claim to be apathetic to religion will buy Shinto traffic safety amulets, have their weddings according to Shinto tradition, and pour their money into annual Shinto festival. The designation "Shinto" sprang up in the eigth century C.E. to distinguish the local religiom from Buddhism, which was being introduced into Japan. "Of course, the Religion of the Japanese '...existed before the introduction of Buddish," explains Sachiya Hiro, a researcher of Japanese religions, "but it was a subconscious religion, consisting of customs and ''mores.' With the introduction of buddishm, however, people became aware of the fact that those mores constituted a Japanese religion, different from Buddhism, which was a foreign religion."
It is difficult to pinpoint a date when the original Shinto, or "Religion of the Japanese," emerged. With the advent of the wetland cultivation of rice, "wetland agriculture necessitated well-organized and stable communities," explains the Kodansha Encyclopedia of Japan, "and agricultural rites-which later played such an important role in Shinto-were developed." Those early peoples conceived of and revered numerous gods of nature.
In addition to this reverence, fear of departed souls led to rites for appeasing them. This later developed into a worship of ancestral spirits. According to Shinto belief, a "departed" soul still has its personality and is stained with death pollution immediately after death. When the bereaved perform memorial rites, the soul is purified to the point of removing all malice, and it takes on a peaceful and benevolent character. In time the ancestral spirit rises to the position of an ancestral, or guardian, deity. Thus we find that the immortal soul belief is fundamental to yet another religion and conditions the attitudes and actions of the believer