As she made her deal with Kyubey to go back in time, Homura Akemi gained control over time itself. She can use her shield to block incoming attacks, but its primary purpose is to allow her to stop time at will. She can keep up the time stop indefinitely, but it slowly drains her magic, thus bringing her closer to despair every second. She can reset the timeline at will to any point in time, but only if at least one month has passed since her last reset. She was never seen resetting it to any point other than waking up the day she met Madoka, as for her task (stopping Madoka from becoming a Magical Girl) this is the farthest back she needs to be. In addition, Homura must activate the shield manually, so if she is unable to do so her timestop becomes unusable. She is also immortal like all the other magical girls as long as her Soul Gem is intact.