A grain of sand will turn back a minute. Harry uses the last time turner to save Severus Snape. The time turner was nestled against Harry's chest, hanging by a thin gold chain, pressed there as Harry leaned against the strong wooden beam supporting the roof of the Shrieking Shack. HP/SS EWE

Unbeknownst to Harry, at the moment of Dumbledore's death, the protection bond known as the Aegis latched onto a new protector. Two years later, Voldemort finally has his hands on his human horcrux and has granted Severus the privilege of breaking him. HP/SS