Here's another interesting quote
Go for the true north, a.k.a. the geographic north. It will make things easier ... unless you are a pilot.
The magnetic north is somewhere in Canada and moves all the time. The difference between the two is called, the magnetic declination. Since the magnetic north moves, the yearly correction that must be added or subtracted is called, the magnetic variation.
Where I live, in Norway, the magnetic declination is nearly null, but at some other places on earth, it can be as much as 30 degrees so it is better, and easier, to keep your compass to the true (geographic) north.
But what about aviation and pilots? Well, all bearings, headings and marking for aviation are given in magnetic north notations. For example the runway 24 is 240 degrees magnetic north. This is because the magnetic compass is still the primary instrument for pilots and, contrary to seafarers who have time to compute the true north of a chart table, the pilot must take quick decisions.
By the way, you will read in some places that the difference between the magnetic and geographic north is called the magnetic variation. That is not true. It is mostly pilots who call it that. It comes from the fact that seafarers use old charts where it is written in the margin, the magnetic declination for the year of publication, then the annual variation. But pilots use new charts all the time. The time between two chart update is actually called, an AIRAC and it happens, internationally, every 28 days!