“Wait till it gets out yeh did it again, Harry. Escaped him, fought him off when he was right on top of yeh!”
--Ruberus Hagrid (DH5)
The Order of the Phoenix strives to relocate Harry from Privet Drive to the Burrow before his seventeenth birthday. They have six people impersonating Harry through the use of Polyjuice Potion, and each Harry Potter has a protector flying with him, with each pair flying to a different safe house. But because Snape planted the idea in Mundungus’s head, and then revealed most of it (except the salient point of seven Harrys) to Voldemort, the Order is ambushed by thirty Death Eaters. An aerial battle ensues. Voldemort is personally fighting, using the wand he had borrowed from Lucius Malfoy, and demonstrating for the first time his power of flight.
Mundungus-as-Harry and Mad-Eye Moody fly north on broomsticks (DH5). Presumably, they are headed for Moody’s house. Voldemort, assuming the real Harry Potter would be with the fiercest protector (Moody), pursues them right away. Mundungus panicks and Disapparates. A curse from Voldemort hits Moody; Moody falls from his broom and dies.
Hermione-as-Harry flies with Kingsley Shacklebolt on thestrals, presumably headed for Kingsley’s house, and are pursued by five Death Eaters, one of whom is Travers. Kingsley claims they injured two of the Death Eaters, and might have killed one (DH5). They are the second target Voldemort pursues, but Voldemort abruptly vanishes to go after Harry and Hagrid.
The real Harry flies with Hagrid on Sirius’s flying motorbike to the Tonks’ house. Hedwig is with them, but is killed by a stray Killing Curse early in the battle. They are pursued by four Death Eaters, one of whom is knocked unconscious early on by a brick wall erupting from the motorbike. Harry is forced to blow up Hedwig’s corpse, along with his prized Firebolt, in the course of battle; this takes out a second Death Eater. The remaining Death Eaters are Selwyn and Stan Shunpike (under the Imperius Curse). Recognizing Stan, Harry uses the Disarming Charm, which gives him away as the real Harry. Voldemort goes after him, but Harry’s wand performs magic of its own accord to destroy Voldemort’s borrowed wand, allowing Harry and Hagrid to crash land in the safe house. Ted Tonks heals him, and sends him to the Burrow via portkey.
George-as-Harry and Lupin fly on broomsticks, and are pursued by Snape (among other Death Eaters). When Snape casts Sectumsempra at a Death Eater’s wand hand, he misses and curses off George’s ear (DH33). The ear is unable to be healed, but George heals completely otherwise.
Ron-as-Harry and Tonks fly on broomsticks to Auntie Muriel’s house. They are pursued by the Lestranges, among others. Ron Stuns a Death Eater, and Tonks injures Rodolphus Lestrange. Bellatrix, who “tried very hard to kill” Tonks, comes out unscathed (DH5). Ron and Tonks miss their portkey and fly to the Burrow.
Fleur-as-Harry and Bill fly north on thestrals and are pursued by half a dozen Death Eaters. They make it to a safe house unharmed, but miss their portkey and have to fly to the Burrow.
Fred-as-Harry and Arthur Weasley fly on broomsticks, and appear no worse for the wear upon taking a portkey to the Burrow.
The battle begins around 9:30 pm, just after dark ("Harry hurried to gather his rucksack, Firebolt, and Hedwig’s cage and followed ... to the dark back garden. On every side broomsticks were leaping into hands"). On July 27, 1997, the sun set at 8:56 in that part of Britain, which means it was about a half hour before it got dark.
Timeline of the Battle of Seven Potters:
8:45 pm - the Dursleys leave Privet Drive just as the sun is setting
8:56 pm - the sun sets
9:15 pm - the Order arrives and preparations are made
9:30 pm - the Dursleys are safely out of range and the Order launches into the sky
9:35 pm - Death Eaters attack
9:40 pm - Hedwig is killed and the battle rages
9:50 pm - Mad-Eye Moody is killed in the skies over Surrey
10:00 pm - Voldemort attacks Harry as they approach the Tonks house
10:15 pm - Harry and Hagrid crash into a pond in the back garden of the Tonks home
11:00 pm - the surviving members of the Order and the decoys gather at the Burrow to heal wounds and mourn the losses