Magnetic North moves. Changing the declared heading of a runway takes an enormous amount, what with all the charts, tables, publications, databases and so on that need to be updated, so it isn't often done immediately the magnetic heading drifts into another "band" so to speak.
Our 31 had recently been changed to 32, which it has technically been for many years. We still get unfamiliar pilots looking to land on 31, to which the a/g operator replies "Ah, it's now 32, but never mind. It still points the same way!"