Meetings for worship and study are held at Kingdom Halls, which are typically functional in character, and do not contain religious symbols. Witnesses are assigned to a congregation in whose "territory" they usually reside and attend weekly services they refer to as "meetings" as scheduled by congregation elders. The meetings are largely devoted to study of Watch Tower Society literature and the Bible. The format of the meetings is established by the religion's headquarters, and the subject matter for most meetings is the same worldwide. Congregations meet for two sessions each week comprising five distinct meetings that total about three-and-a-half hours, typically gathering mid-week (three meetings) and on the weekend (two meetings). Prior to 2009, congregations met three times each week; these meetings were condensed, with the intention that members dedicate an evening for "family worship". Gatherings are opened and closed with kingdom songs (hymns) and brief prayers. Twice each year, Witnesses from a number of congregations that form a "circuit" gather for a one-day assembly. Larger groups of congregations meet once a year for a three-day "regional convention", usually at rented stadiums or auditoriums. Their most important and solemn event is the commemoration of the "Lord's Evening Meal", or "Memorial of Christ's Death" on the date of the Jewish Passover.