UTC is maintained via leap seconds, such that DUT1 remains within the range −0.9 s < DUT1 < +0.9 s. The reason for this correction is that the rate of rotation of the Earth is not constant, due to tidal braking and the redistribution of mass within the Earth, including its oceans and atmosphere.
Forecast values of DUT1 are published by IERSBulletin A. Weekly updated values of DUT1 with 0.1 s precision are broadcast by several time signal services, including WWVB.