A week starts with Monday (day 1) and ends with Sunday (day 7).For example, the first week of the year 1997 lasts from 1996-12-30 to 1997-01-05 and can be written in standard notation as for applications like industrial planning where many things like shift rotations are organized per week and knowing the week number and the day of the week is more handy than knowing the day of the month.2/4/95, 4/2/95, 95/2/4, 4.2.1995, 04-FEB-1995, 4-February-1995, and many more.Especially the first two examples are dangerous, because as both are used quite often in the U. and in Great Britain and both can not be distinguished, it is unclear whether 2/4/95 means 1995-04-02 or 1995-02-04.Note: The value 60 for ss might sometimes be needed during an inserted leap second in an atomic time scale like Coordinated Universal Time (UTC).A single leap second is inserted into the UTC time scale every few years as announced by the International Earth Rotation Service in Paris, to keep UTC from wandering away more than 0.9 s from the less constant astronomical time scale UT1, which is defined by the actual rotation of the earth.
For example, the fourth day of February in the year 1995 is written in the standard notation as Other commonly used notations are e.g.Especially authors of Web pages and software engineers who design user interfaces, file formats, and communication protocols should be familiar with ISO 8601.Contents: Date, time of day, time zone, software hints.It is not intended as a replacement for language-dependent worded date notations such as “24.Dezember 2001” (German) or “February 4, 1995” (US English).However the 12 months of a year are of some obscure mystic origin and have no real purpose today except that people are used to having them (they do not even describe the current position of the moon).In some applications, a date notation is preferred that uses only the year and the day of the year between 001 and 365 (366 in leap years).ISO 8601 should however be used to replace notations such as “2/4/95” and “9.30 p.m.”.Apart from the recommended primary standard notation YYYY-MM-DD, ISO 8601 also specifies a number of alternative formats for use in applications with special requirements.Possible ISO week numbers are in the range 01 to 53. (There is one historic exception: the year in which the Gregorian calendar was introduced had less than 365 days and less than 52 weeks.) Proof: Per definition, the first week of a year is W01 and consequently days before week W01 belong to the previous year and so there is no week with lower numbers.Considering the highest possible week number, the worst case is a leap year like 1976 that starts with a Thursday, because this keeps the highest possible number of days of W01 in the previous year, i.e. In this case, the Sunday of W52 of the worst case year is day number 4 51*7=361 and 361-366=5 days of W53 belong still to this year, which guarantees that in the worst case year day 4 (Thursday) of W53 is not yet in the next year, so a week number 53 is possible.In addition, these formats have several important advantages for computer usage compared to other traditional date and time notations.The time notation described here is already the de-facto standard in almost all countries and the date notation is becoming increasingly popular.An abbreviated version of the year and week number like is sometimes useful as a compact code printed on a product that indicates when it has been manufactured.