The Haabʼ was made up of eighteen months of twenty days each plus a period of five days ("nameless days") at the end of the year known as "Wayeb"' (or "Uayeb" in 16th-century orthography). The five days of Wayebʼ were thought to be a dangerous time. Foster (2002) writes, "During Wayeb, portals between the mortal realm and the Underworld dissolved. No boundaries prevented the ill-intending deities from causing disasters." To ward off these evil spirits, the Maya had customs and rituals they practiced during Wayebʼ. For example, people avoided leaving their houses and washing or combing their hair. Bricker (1982) estimates that the Haabʼ was first used around 550 BC with a starting point of the winter solstice.