Professor McGonagall did. Because she is the one who requested the Ministry of Magic to give a Time Turner to Hermione in the first place, insisting that Hermione is a model student and that she would never use the device for anything other than her classes. Oh well. Dumbledore also knew, obviously.
Why did McGonagall trust Hermione with the Time-Turner?
Perhaps McGonagall saw Hermione's potential and knew that someone like her could show that the Time-Turner had applications for students looking to take on extra credit at school or, in the case of Prisoner of Azkaban's finale, save innocent people from evil.
Since McGonagall made her swear to not tell anyone about it, she did not mention it to Harry Potter or Ron Weasley until the end of the school year, when she and Harry used it to travel back in time and save Sirius Black and Buckbeak from certain death.
As Sirius Black had no idea that the Time Turner existed, they must've found it unlikely that Sirius confunded them with instructions to use the Time Turner to save him.
The Time Turner - Harry Potter and the Prisoner of Azkaban HD
Is Ron older than Harry?
Ron is the same age as Harry in the books and films due to being in the same school year, meaning Grint was one year older than Ron's age of 11 when filming Harry Potter and the Sorcerer's Stone.
The time turner couldn't have been used to save Harry's parents because it was too far back in time; you cannot go back more than five hits without there being very bad consequences.
Why didn't Hermione use the Time-Turner to save Sirius?
Changing the past is hazardous and apparently nigh impossible. Buckbeak could be rescued because he already had been rescued, while Sirius was seen to have died by several witnesses. Even if it were possible, Hermione only had the Time Turner for one year.
When questioned by Bellatrix about his loyalties, Snape says he has been working for Voldemort ever since Voldemort's return, and explains his actions in the previous books in that light. He points out that gaining Dumbledore's trust and protection has kept him out of Azkaban and free to operate on Voldemort's behalf.
Hermione explains that the hourglass is a Time-Turner; she has been using it all year to get to all her classes. Professor McGonagall instructed her to tell no one about it.
Ron first began to show signs of romantic interest in Hermione in their second year; he was irritated by her crush on Professor Gilderoy Lockhart, became so angry when Draco Malfoy called her a "Mudblood" that he tried to hex him, and was even more upset than Harry when she was one of the Basilisk's victims.
In the film, she only hugs Harry, and just gives a hesitant handshake to Ron (Note: This was the result of Emma Watson being hesitant to hug both Daniel Radcliffe and Rupert Grint in public view, with her hugging Radcliffe during filming having to be frozen for a few seconds to get the desired effect due to Watson ...
Why didn't they use Time-Turner to stop Voldemort?
These instances followed Rowling's stance on self-fulfilling prophecies. With the established Harry Potter time travel rules, Harry and his friends never had the option of traveling back in the past to kill Voldemort. If they were to do so, Voldemort would already be dead in the present timeline.
Thinking about her future, she realised that wedding a Muggle who didn't know that she was a witch would mean Minerva would follow her mother's footsteps and live unhappily with her wand locked away, shredding all of her ambitions.
Other than Pansy Parkinson with absolute zero room-reading skills and Professor McGonagall sending all the Slytherins to the dungeons, from what I understand McGonagall literally had them locked up in the dungeons cells than give them a choice whenever to fight against Voldemort or remain in the common room, because ...
The prolonged misery of being exposed to dementors kept the prisoners locked within their own minds, so Sirius lost the ability to transform. However, Sirius explained that the knowledge of his innocence kept him sane in a way most of Azkaban's prisoners were not.
Dumbledore's lack of belief that Sirius is innocent is also suspect. Sirius was a member of the Order of the Phoenix which fought against Death Eaters, but Sirius also was as close to James as a brother, the Potters even took him in when he ran away from home.
J.K. Rowling addressed the time-turner plot holes by introducing limitations on time travel and ultimately destroying all time-turners. The destruction of all time-turners in "Order of the Phoenix" prevented further use and solved the plot holes in a messy way.
He hid them using the only thing that would work against Voldemort. He used Fidelius charm and after that even secret keeper was to be protected using that as Sirius said in PoA. The plan failed because wormtail who was their secret keeper betrayed them.
Dumbledore didn't know that Sirius was innocent. He knew there was a spy within the Order of the Phoenix and after Snape passed along the prophecy to Voldemort he knew that there was a danger to the Potters. He also knew there as a danger to the Longbottoms as well since Neville fit the details of the prophecy too.
Severus Snape wanted to teach D.A.D.A. for years, but Albus Dumbledore denied him the job repeatedly, partly for fear of Snape straying back towards the darkness, and partly to keep him around for longer, given the curse on the position. Snape finally got his wish in Harry's sixth year, taking over D.A.D.A.
Luna married fellow naturalist Rolf Scamander, grandson of Fantastic Beasts and Where to Find Them author Newt Scamander, considerably later in life than Harry, Ron, Hermione, and Ginny, who all married and started families in their early-to-mid twenties.
Rowling elaborated on Ginny's future after the release of the book, saying that after leaving Hogwarts, she joined the Holyhead Harpies and, after spending a few years as a celebrated player, retired to become the senior Quidditch correspondent at the Daily Prophet, and to start a family with Harry.
