Parachronisms are usually seen as objects or ideas which were once common, but are now considered rare or inappropriate. They often take the form of obsolete technology or outdated fashion. This is different from an anachronism, in which the object or idea in question had not yet been invented when the situation takes place, and is therefore impossible to have existed at that time. Thus a suburban housewife in the United States around 1960 would not ordinarily use a washboard for laundry after washing machines became the norm, and few teenagers of that time would be listening to ragtime music.
The time in which a practice would be a parachronism could be temporary; the music of Johann Sebastian Bach went into nearly-complete oblivion during the late 18th Century and would not likely be performed in public until it was revived in the middle of the 19th Century. It would not be a parachronism in the late 20th Century, when millions deliberately listened to music associated with earlier times. Likewise, one would hardly expect a college professor in Nazi Germany to extol the liberal ideas of Thomas Jefferson or the socialist ideals of Karl Marx and avoid unpleasant consequences, although such expression would be permissible in either the Weimar Republic before 1933 or the Federal Republic of Germany after 1949.