There is a claim from a Muslim PDF that Chinese astronomers observed Mohammed's "splitting of the moon".
The claim states: "The splitting of the moon event which occurred in the 7th Century CE was recorded by the Chinese astronomers. The event happened at the time of Sun Wu Kong (the Chinese King). It resulted in a broad sweeping change of the Calendar in China, the Chinese astronomers recorded that the year became longer by 5 days due to the reorganization of the phases of the moon. Thus, China was also affected at the 7th Century CE at the time of the split moon event.".
The same website also claims calendar changes occurred in Babylon and Copan around the same time in the early 7th century CE.
Im not religious, but I would like to investigate these claims.
The source of the claim is on page 16: https://www.scribd.com/document/286086546/The-Splitting-of-the-Moon
The first red flag that this claim is completely spurious is that Sun Wukong is not a historical 'king of China,' but the Monkey King of Chinese literature and folklore. The actual rulers of early 7th-century China were Yang Guang (known posthumously as Emperor Yang of the Sui dynasty) until 618, then Li Yuan (Emperor Gaozu of Tang) until 625, and lastly Li Shimin (Emperor Taizong of Tang) until well after the death of Muhammad. Sun Wukong is most widely known as a hero in the novel Journey to the West (Xiyouji), a 17th-century novel inspired loosely by the travels of the Tang Buddhist scholar Xuanzang in the 630's. This is his only relation to the early 7th century and to misconstrue the fictional, super-powered monkey famous throughout East Asian culture as being an actual historical figure, and an emperor no less, shows that very little effort was put into making this claim appear convincing.
Still, for the sake of thoroughness I examined the court histories, Book of Sui, Old Book of Tang, and New Book of Tang, for references to calendar reform or to major astronomical phenomena during this period. Astronomy and the calendar were important enough subjects to the Chinese states that official histories typically devoted an entire section to each (alongside sections on topics like criminal law, geography and bureaucratic structure), so if such things happened we can be fairly confident that they would be recorded in these histories. There was, in fact, a new calendar propagated in 619 by the aforementioned Li Yuan, founding emperor of Tang, but the sources state explicitly that this was done to mark the establishment of the new dynasty and was not in response to any astronomical event or to any perceived shortcoming in its predecessor. This was a common practice for new Chinese regimes and that the Sui-Tang transition aligns roughly with the latter part of Muhammad's lifetime is coincidental.
So, in short, the claim has no basis in Chinese sources and, by citing a well-known fictional character in place of any real historical figure, betrays a total disinterest in persuading anyone with a passing knowledge of Chinese history or culture.