Like other cultures of Mesoamerica, the Maya used a 260-day calendar, referred to as the Tzolk'in. The length of this calendar coincides with the average duration of human gestation. Its purpose is to provide guidance in life through a consideration of the combined aspects of the 20 named days and 13 numbers, and to indicate the days on which sacrifice at certain 'number shrines' might lead to desired results. The days were commonly deified and invoked as 'Lordships'. The general Yucatec word for 'priest' (ah k'in) referred to the counting of the days. Within the social group of the priests at court, it was customary to pass the 'burden' of the time-units on from one divine 'number bearer' to the next.