Here's why:
* Ancient Observations: Records of Halley's Comet sightings date back to at least 240 BC in China. These observations were just records of a bright, unusual object in the sky, not an understanding of it as a recurring comet.
* Edmund Halley's Contribution: Edmund Halley in 1705 calculated the orbits of a number of comets, and realized that sightings in 1531, 1607, and 1682 were likely of the same object returning. He predicted its return in 1758, which proved to be correct, solidifying its identification as a periodic comet.
Therefore, while observations go back centuries, we can say that Halley's Comet was identified as a recurring object in 1705 by Edmund Halley.
