It makes sense that it's going to come out of the highest occupied atomic orbital, because that's going to be the lowest amount of energy that's required to actually eject an electron.

从最高占据轨道上,去掉一个电子是合理的，因为这样是发射一个电子,所损失的最低能量。

麻省理工公开课 - 化学原理课程节选

Over a few decades this would amount to a minute's difference, but over several hundred years this would mean the atomic clock time-scale and the time-scale based on the Earth's rotation would be out by an hour.

BBC: Changes to the world's time scale debated