Dendrochronology is a dating technique that makes use of tree growth rings. This annoys me. While K-Ar dating requires destroying large samples to measure potassium and argon levels separately, Ar-Ar dating can analyze both at once with a single, smaller sample. Before the advent of absolute dating methods in the twentieth century, nearly all dating was relative.
In recent years, a few of these methods have undergone continual refinement as scientists strive to develop the most accurate dating techniques possible.