As we have repeatedly stated, the Satanist believes that numbers contain inherent power.Thus, they literally order their lives by occult numerology – such numerology also is a key component in astrology, another system of divining that Satanists observe very closely. The occult calendar is divided into four (4) segments of 13 weeks each.

Source: Occult Holidays and Sabbats: Why Holidays are Satanic Rituals – Prepare for Change