Lily Evans and James Potter finish Hogwarts and immediately go to work for The Order of the Phoenix (OBT/CH). Voldemort tried to recruit them to be Death Eaters (PC/JKR1), but both were defiant. Lily and James probably got married in the Summer or Fall of 1978, though it could have been as late as the summer of 1979.
Fall 1979 Sybill Trelawney makes a prophecy to Albus Dumbledore about a child to be born in July of that year. Partially overheard by a Death Eater, Severus Snape, who reports what he heard to Voldemort.
circa October 1979 Lily becomes pregnant with Harry, and both she and James go into hiding because of the prophecy (OBT/CH).
July 1980 Two children are born who fit the prophecy's criteria: Harry Potter and Neville Longbottom. Dumbledore knows that they are in danger, but hesitates to act until he knows more about what Voldemort might do.
between July 31 and September 1, 1980 Severus Snape discovers that Lily and her infant son have been targeted by Voldemort, has a crisis of conscience, and tells Albus Dumbledore. Snape offers his allegiance to Dumbledore in exchange for protection for Lily and is given the position of Hogwarts Potions Master.
before October 24, 1981 Approximately a week before the attack, Dumbledore suggests that the Potters use the Fidelius Charm to protect their hiding place. The Charm's Secret Keeper was initially supposed to be James’ best friend Sirius Black. However, Sirius persuaded the Potters to bluff and use Peter Pettigrew instead (PA19). Unfortunately, Pettigrew had become a servant of Voldemort and he betrayed their hiding place to him. A week after the Charm was first performed, Lily and James are attacked by Lord Voldemort.
Monday*, October 31, 1981, nighttime at Godric’s Hollow
*October, 31, 1981 was in reality a Saturday, not a Monday. Man’s voice: "Lily, take Harry and go! It’s him! Go! Run! I’ll hold him off ------"
Lily goes to Harry's room where he is in his cot [crib].
According to Voldemort, James died "straight-backed and proud." (GF34)

The sounds of someone stumbling from a room -- a door bursting open -- a cackle of high-pitched laughter -- (PA12)
Lily’s voice: "Not Harry, not Harry, please not Harry!"
Voldemort: "Stand aside you silly girl … stand aside now."
Lily: "Not Harry, please no, take me, kill me instead ----- "
Lily: "Not Harry! Please … have mercy … have mercy… "
Harry hears a shrill voice laughing and the woman screaming (PA9, PA12).

Then Harry remembers a blinding green flash and a burning pain in his forehead, then a high, cold cruel laugh. Voldemort had used the Killing Curse on Lily and Harry.