The most common, most accurate way to find the age of a tree is to count the number of rings visible when their trunk is cut horizontally. Each year, most trees add an extra layer of growth to their trunks. Over time, their trunks get thicker and thicker.

How far back can Tree-ring dating go?

Each ring marks a complete cycle of seasons, or one year, in the trees life. As of 2020, securely dated tree-ring data for the northern hemisphere are available going back 13,910 years.