Hannah Goodheart and the Guardian of Time - Hannah Goodheart, #1

Turning thirteen can be difficult - especially when a time-traveling thief steals your necklace, and a brewing temporal conflict turns your birthday party into a mission to save the universe. As Hannah and her friends chase the thief across time and space, they learn her necklace is more than a pretty piece of jewelry. Only one person can control the powerful pendant, and they must find them before the entire universe is wiped from history.
Myth and magic collide in Hannah Goodheart and the Guardian of Time