https://www.sciencedaily.com/releases/2018/05/180529103555.htm

A time crystal is a structure that does not repeat in space, like normal three-dimensional crystals such as snowflakes or diamonds, but in time. In practice this means that crystals constantly undergo spontaneous change, breaking the symmetry of time by achieving a self-sustaining oscillation.

The value is in the time crystal's coherency, a property that allows temporal and spatial consistency, amounting to longevity otherwise not possible.