The major time divisions of classical music up to 1900 are the early music period, which includes Medieval (500–1400) and Renaissance (1400–1600) eras, and the Common practice period, which includes the Baroque (1600–1750), Classical (1750–1830) and Romantic (1804–1910) eras. Since 1900, classical periods have been reckoned more by calendar century than by particular stylistic movements that have become fragmented and difficult to define. The 20th century calendar period (1901–2000) includes most of the early modern musical era (1890–1930), the entire high modern (mid 20th-century), and the first 25 years of the contemporary or postmodern musical era (1975–current). The 21st century has so far been characterized by a continuation of the contemporary/postmodern musical era.
Is there an answer to this question (If it cannot be answered, say "unanswerable"): What era has the 21st century has been characterized by?
the contemporary/postmodern musical era