Good morning. You are one day closer to the end of the world. You have been warned.
Robert Thorn (Gregory Peck) is a wealthy American ambassador, expecting his first child with wife Katherine (Lee Remick). When Katherine's child dies during birth, however, Robert switches it with another child to spare his wife the tragedy. 5 years later, the child's nanny openly hangs herself for Damien. It's all for you, Damien!
Damien is born on June 6th. The year is not stated, though implied through dates mentioned in the sequels. However, these dates (particularly those provided in the third film) are highly inconsistent.