Decade ("60s" or "sixties"), although this may leave it uncertain which century is meant. These references are frequently used to encapsulate popular culture or other widespread phenomena that dominated such a decade, as in "The Great Depression of the 1930s" or "The Roaring Twenties". However, the Gregorian calendar begins with the year 1. (There is no year "zero", and the year before AD 1 is 1 BC with nothing in between.) Therefore, its "first" decade is from AD 1 to AD 10, the "second" decade from AD 11 to AD 20, and so on. So, although "the 1960s" comprises the years
1920s in Western fashion in the early part of the decade, change was slower, and there was more reluctance to wear the new, revealing styles made popular. From 1925, the public more passionately embraced the styles now typically associated with the Roaring Twenties. These styles continued to characterise fashion until the worldwide depression worsened in 1931. After World War I, the United States entered a prosperous era and, as a result of its role in the war, came out onto the world stage. Social customs and morals were relaxed in the optimism brought on by the end of the war and the booming of