'Id. The term 'id, meaning "day of celebration," was introduced by the Prophet Muhammad to designate the two annual Islamic celebrations prescribed in the Qur'an verse 2: 67: "Unto each nation have We given sacred rites which they are to perform; so let them not dispute with thee of the matter, but summon thou unto thy Lord. Lo! thou indeed followest right guidance." The greater of the two celebrations is 'Id al-Adha, the feast of the sacrifice, and the lesser is 'Id al-Fitr, the feast of breaking the fast. The dates of these two celebrations are determined by the lunar calendar, so they shift in the solar calendar by about eleven days each year. Thus, over several decades, they rotate through the seasons.

Jum'ah. Friday is the day of jum'ah, or congregational prayer. This day is not, as in the Jewish...