What are the fundamental limits on our ability to measure time according to quantum theory and thermodynamics? Can they change our usual notion of watches? It’s time to rethink time and its fundamental limitations. Temporal crystals may hold the key to these questions. These peculiar phases of matter are characterized by a surprisingly stable and precise temporal ordering structure among their microscopic constituents, thus offering a fascinating playground for unravelling such questions.

We will explore the role of time crystals as the main working substance of an autonomous quantum clock, studying its performance in connection with quantum laws (uncertainty principles) and thermodynamics (irreversible entropic processes). The collective, many-body dynamic nature of time crystals can radically influence the operation of a quantum clock, pushing our limits to timekeeping.