What Decade Is This Date?


dĕ-sĕn′ē-əl | /dɪˈsɛnɪəɫ/


  1. Happening once every ten years.
  2. Related to a ten-year period.


  1. The tenth anniversary of an event.
  2. An event that occurs every ten years.

A decennial is essentially the same concept as a biennial except it happens once every ten year—i.e., every decade—instead of every other year. You can tell this be the prefix. "bi-" is the Latin prefix for two, and "dec-" is the prefix for ten.


The US Census is one of the biggest decennial events. Beginning in 1790, the census has continued to happen every ten years since then. Many other countries follow this frequency, including the United Kingdom, Singapore, Kenya, Austria, Chile, and Romania.
Super Blooms
A decent example of a decennial event is the super bloom of wildflowers in Death Valley. While not always exactly ten years, the trend is for it to happen once a decade.