The Hajj (First two days) - Waqf al Arafa or Hajj Day then the Eid (sacrifice of Abraham)

from Religion and Ethics Newsweekly (PBS dot-org, Lilly Foundation is sponsor):

Hajj (Islam)
Hajj is the pilgrimage to Mecca, occurring on the 7th-12th days of the month of Dhu al-Hajja in the Islamic calendar. This is the largest annual pilgrimage in the world, and all able-bodied Muslims are required to participate at least once in their lifetimes. Several rituals are performed during this pilgrimage, including walking counter-clockwise seven times around the Kaaba, a cube-shaped building representing the Muslim direction of prayer, and drinking from the Zamzam well.

November 5

Waqf al Arafa – Hajj Day (Islam)
Waqf al Arafa is the Islamic observance day during Hajj when pilgrims pray for forgiveness and mercy. Pilgrims stay awake at night to pray on the hill of Arafat, the site where Muhammad traditionally delivered his last sermon.

November 6

Eid-Ul-Adha (Islam)
Concluding the Hajj, Eid-Ul-Adha is the Festival of Sacrifice held the day after the visit to Arafat, when pilgrims move to Mina. Those who can afford to do so sacrifice their best domestic animals, such as sheep or cows. This practice recalls Abraham’s willingness to sacrifice his son in obedience to God, and it commemorates God’s forgiveness.