It is amazing that they can model the earth to that level of detail! It wouldn't affect the accuracy of the cesium clocks themselves, more likely what would happen is that UTC would be adjusted as needed (see wikipedia, usno.navy.mil, etc. for UTC or Coordinated Universal Time for nauseatingly detailed description - leap seconds are periodically added to account for the slowing rotation of the earth). This serves as the basis for time standards such as the USNO and Internet Time, so it gets propagated out to the net timer servers and radio time beacons and thus to all the Casio / Citizen / etc. radio controlled watches / clocks.