Date and time notation in the United Kingdom
Dates are written traditionally in "day month year" order, using a stroke as the separator. This order is used in both the traditional all-numeric date (e.g., "31/12/99") and the expanded form (e.g., "31 December 1999"). Writing the day of the month as an ordinal number (e.g., "31st of December") is also common - and since the advent of automatic correction in word processors, the ordinal indicator has been lifted into superscript (e.g., "31st of December") in typed documents, to match the handwritten style.
When saying the date, it is usually pronounced using the ordinal number of the day first, then the word "of" then the month (e.g., "the 31st of December 1999"). The month-first form (e.g., "December the 3rd") was common a hundred years ago and may still be spoken when not including a year in the sentence but is now less frequently used.
Using either form in purely numeric form, leads to confusion as the DMY MDY forms are ambiguous for days-of-the-month 1 up to 12.
The "day month year" order is also the case in modern Welsh (e.g., "20 Mai 1999", "20fed Mai 1999", "20fed Mai 1999"). The "month day year" order (e.g., "Mai 20, 1999") was previously more common than it is nowadays, it not being unusual to see a Welsh "month day year" date next to an English "day month year" date on a bilingual plaque from the latter half of the 20th century. "20 Mai 1999" is read as "yr ugeinfed o Fai mil naw naw naw", with the usual soft mutation of M to F after "o" (of). 1999 can be read as either "mil naw naw naw" (thousand nine nine nine) or "un naw naw naw" (one nine nine nine).
Weeks are generally referred to by the date on which they start, referring to the Monday, e.g., "week commencing 5 March". ISO 8601 week numbers are found in diaries and are used in business.
ISO 8601 has been adopted as British Standard BS ISO 8601:2004, and is popular in specialist use (e.g., use-by dates on medical products) and computer applications e.g. database systems, communication protocols, web pages, and so forth. The appearance of such big-endian dates is increasing especially with computer-generated forms and invoices, as well as simply internet-accessible content in an age of Globalization.
Both the 12-hour and 24-hour notations are used in the United Kingdom. The 12-hour notation is still widely used in ordinary life, written communication and displays, and continues to be used in spoken language. The 24-hour notation is used in timetables and in some computer applications; computers running Microsoft Windows with UK regional settings default to display time in 24-hour notation. The 24-hour notation is used more often than in the United States especially for bus, train and airline timetables, but not quite as commonly as in much of the non-English speaking world. To separate hours and minutes, either a dot (e.g., 10.00pm) or a colon (10:00pm) can be used. To separate hours, minutes, and seconds, a colon (10:00:15) is normally used.
In British English, the expression "half hour" is used colloquially to denote 30 minutes past the hour. For example, "half ten" means "10:30". This contrasts with the Dutch, German, Hungarian, Czech, and Scandinavian languages, where the same type of expression denotes 30 minutes before the hour.
The Welsh language usage of the 12-hour and 24-hour clocks is similar to that of UK English above. However, the 24-hour notation is interesting in that it only has a written, not a spoken form. For example, written 09.00 and 21.00 are both said ("naw o'r gloch" nine o'clock, literally nine of the bell). Minutes are always either "wedi" (after) or "i" (to) the hour, e.g., 21.18 "deunaw (munud) wedi naw" (eighteen (minutes) past nine) and 21.42 "deunaw (munud) i ddeg" (eighteen (minutes) to ten). Phrases such as "y bore" ((of) the morning), "y prynhawn" ((of) the afternoon) and "yr hwyr" ((of) the evening) are used to distinguish times in 12-hour notation, much like Latin "am" and "pm", which are also in common use, e.g., 9.00yb (09.00) as opposed to 9.00yh (21.00).
- International Standard ISO 15223: Medical devices – Symbols to be used with medical device labels, labeling and information to be supplied