Definitions vary. The formal Regency period was nine years. But, from Wikipedia: "The term Regency (or Regency era) can refer to various stretches of time; some are longer than the decade of the formal Regency, which lasted from 1811 to 1820. The period from 1795 to 1837, which includes the latter part of George III's reign and the reigns of his sons George IV and William IV, is sometimes regarded as the Regency era, characterised by distinctive trends in British architecture, literature, fashions, politics, and culture."