chronogram

From chrono- +‎ -gram, from Ancient Greek χρόνος (khrónos, “time”) + γράμμα (grámma, “writing”).

chronogram (plural chronograms)

1. A sentence or inscription whose letters, when interpreted according to a system (such as Roman numerals) in which letters correspond to numeric values, stand for a particular date (usually the date of inscription) when rearranged.
2. (genetics) A phylogenetic tree that has branch spans proportional to evolutionary time.

   Coordinate term: phylogram