The Babylonian astrologers had calculated with remarkable accuracy the coming of the star of the Messiah. They expected the birth of the "ruler of the world" to occur in or after 7 B.C., which is precisely when the Virgin of Nazareth was alive!
Kepler, one of the fathers of modern astronomy, observed in December 1603 the very bright conjunction (perfect alignment) of Jupiter and Saturn in the Pisces constellation. Thanks to his calculations, he established that the same phenomenon (which causes an intense and bright light in the starry sky) should also have occurred in 7 B.C., and then discovered an ancient commentary on Scripture by Rabbi Abarbanel, recalling that, according to a Jewish belief, the Messiah was to appear precisely when, in the constellation of Pisces, the light of Jupiter and Saturn would become one!
Now for the Babylonian astrologers, this conjunction, which is observed only once every 794 years, had occurred three times in 7 BC: on May 29, October 1, and December 5. They therefore considered the constellation of Pisces to be the sign of the end of time, meaning the beginning of the messianic era.