The Samaritan calendar is a lunisolar calendar with 354 days. It is divided into 12 months of 29 or 30 days each. The months do not have names, but are designated by ordinal numbers (for instance, the first month, the second month, etc.). In order for the primarily agrarian feasts to be celebrated in the same season each year, an intercalation system is used (in other words, at certain times an additional month is added). The Jewish and Samaritan methods of intercalation differ from each other, so the dates for celebrating Passover do not always coincide.