On Tue, 05 Jan 2016 16:15:26 -0800
OFWW wrote:

Did you know that tree rings do not show years, but show rainy
seasons?

it is not that simple
some can be decades and longer
as always it depends on many factors

dendrochronology is the study of the rings

there are photos of giant sequoia cross sections marked with historic
events that are fun to see