What is the ruling on cutting hair according to the lunar calendar, and is it related to belief?

It is not permissible to cut hair according to the lunar calendar, because that is among the forbidden attachments to stars, and they do not affect the length or density of hair, nor do they improve it. Whoever believes that stars affect by themselves is a disbeliever (kafir), and whoever believes that they are a cause is guilty of minor polytheism (shirk asghar). Stars are used only to determine time, such as the times of seasons, and have no effect on the occurrence of cold or heat or the quality of crops. The claim that cutting hair on a specific day benefits its length is astrology and sinful, and it oscillates between major disbelief and minor polytheism depending on the belief in the star's influence. The Messenger of Allah, peace and blessings be upon him, mentioned that whoever acquires knowledge from the stars has acquired a branch of sorcery. Stars were created for three purposes: as an adornment for the sky, as projectiles against devils, and as signs by which people are guided. Whoever interprets them otherwise has erred. The science of stars is divided into the science of influence (ilm al-ta'thir) – which is major polytheism if one believes they create events, or disbelief if one claims knowledge of the unseen through them, or minor polytheism if one believes they are a cause for the occurrence of good and evil – and the science of navigation (ilm al-tasyir) – which is permissible for inferring religious and worldly benefits such as directions and seasons. In summary, stars have no effect on the length or beauty of hair, and this belief is from soothsaying.