Yes, the earth’s magnetic field changes with time. Anyone who has kept track of magnetic declination changes over the last few decades knows this. These data from about 1000 years ago are fascinating, though.
Yup, the compass adjustment for true north has changed just since I was a Boy Scout. The Scouts really tightened up membership after I was done with ‘em.
https://freerepublic.com/tag/poleshift/index