morphological, and phonological data. Chronology can be found but there is no absolute date estimates utilizing this system.

Glottochronology enables absolute dates to be estimated. Shared cognates (cognates meaning to have common historical origin) are calculate divergence times. However the method was found to be later discredited due to the data being unreliable. Due to this historical linguists have trouble with exact age estimation when pinpointing the age of the Indo-European language family.