If the soil is low in nutrients and climate is harsh, trees grow slower than in more favourable conditions can be more than hundred years old but only couple of meters in length. You can estimate the age of a young pine with sufficient accuracy by counting the number of branch whorls (see the adjoining picture) and add about three years.
When you estimate the age of a fully-grown pine this method become inaccurate because pine is a photophilous (sun) plant and when it grows larger it drops the lower branches. Then it is best to use a hollow drill. You drill it trough the middle of the tree and from the sample you get, you can count the annual growth ring. The rings are readily distinguished because of differences in the cells formed during the early and late parts of the season. Springwood is faster growing and lighter coloured than more slowly growing summerwood. During the winter trees naturally don’t grow.
Try to estimate the age of the forest surrounding you!