Are weather vanes oriented true or magnetic?

On a recent LAX layover, my F/O stood me up so I walked to Manhattan Beach where there is a pier with a small aquarium at the end. On its roof is a weather vane which triggered a thought…are weather vanes oriented to true or magnetic north? Did the builder wait until sunrise or sunset to figure a true heading or did they use a compass to tweak things to magnetic? I notice my smartphone swings both ways with the compass App. I forget how I oriented my weather vane when I built a shed with a cupola/weather vane. Probably just winged it.

P.S There are signs at the beach stating you are not allowed to kill great white sharks.