The changeover to decimal currency
. The word could also mean any conversion to decimal
, such as metrication
of weights and measures, or changing hex or binary numbers to decimal, but in practice it refers to the eventual conversion of the British currency
and the same system in other Commonwealth
countries. Britain went over to decimal on 15th February 1971
. Australia had done so in 1966, and most of the Commonwealth changed over around those years too.
The old currency was 12 pence (plural of penny) = 1 shilling, 20 shillings = 1 pound. A large amount was written as e.g. £5 10s. 6d. An amount of just shillings and pence could also be written e.g. 2/6 for 2s. 6d. (pronounced "two and six"), and 2s. bare could be 2/- (never 2/0). Tables of conversion filled the backs of books like logarithm tables.
I don't know what the first decimal currency was, but in 1704 Tsar Peter the Great of Russia created the system that remains to this day, 100 kopecks = 1 rouble. The decimal system was popularized by the rational reforms of the United States and the French Revolution, and spread to the rest of the world (along with the metric system in most places): by the early 1900s only the British Empire was unconverted. I'd be curious to know if there were any other countries that kept non-decimal systems, as I can't think of any.
Actually Britain got into the act in 1849 by issuing the florin or two-shilling coin (one tenth of a pound). This was intended to pave the way for decimalisation, but it never eventuated. However, Canada did adopt dollars and cents in the mid nineteenth century, doubtless because they were next door to the USA.
Most countries changed the name of their currency on decimalisation (to dollars and cents in many), but Britain retained both pound and penny and dropped only the shilling. Instead of 240 pence = 1 pound it became 100 pence = 1 pound. We chose to keep the pound the same, and its subdivision was originally called the new penny, symbol p instead of the old symbol d (Latin denarius). About ten years afterwards, the word "new" was dropped from coinage, but the penny is now almost always called "pee", not penny.
The shilling and two-shilling (florin) pieces were renamed several years before decimalisation, since 1/- = 5p and 2/- = 10p exactly, but other old coins had to be scrapped: the halfpenny, penny, threepence, and sixpence. (The farthing or quarter of a penny had been abolished in the early 1960s.) Instead we got a half new penny (which has since disappeared, being worthless), and 1p, 2p, 20p, and 50p coins.
Given a currency of 240 pence = 1 pound, there are two ways to decimalise it. We chose to retain the pound as is, and revalue the new penny to a hundredth; and this is what was begun with the 1849 florin. The alternative method was proposed in 1887: proofs of a ducat of 100 existing pence (8/4) were issued, but the currency was never put into circulation.