Date

¸attributedate

Computer files should always carry a date-and-time¸time stamp¸date stamp stamp to record time of the last modification. Some file systems even store date-and-time stamps for last read, last write, last backup, and so on.

Unfortunately, many computers do not have a reliable time standard, and if they lack a network connection, have no way of maintaining a correct one. Date-and-time stamps are recorded in the file system, rather than the file itself, and are usually lost when the file is transferred to another system. That is regrettable, but it is a fact of life we still have to tolerate.

Consequently, a standard file header should carry a date and time. The editing support described here supplies it in the form

%%%     date            = "07 October 1991",

Dates and times are expressed in a variety of formats that depend on the country and culture.¸datecultural dependence¸timecultural dependence Some software can deal with a considerable variety of formats, ranging from ``last Wednesday'' to ``1991.11.06:12.34.17''. The important point is that the encoding must be unambiguous . In particular, forms like 12/06/91 should be avoided: does it mean the 12th day of the 6th month, or the 6th day of the 12th month? The year should not be abbreviated to two digits; the new millennium is not far away.

From version 1.30 of this package, dates in the ISO form 1996/04/17 are also recognized. update-date¸update-date will preserve that style in existing date fields, and generate it in new ones if the variable file-header-ISO-date-style¸file-header-ISO-date-style is non-nil. The field separator character, normally a slash, is determined by the first character of the string stored in the variable file-header-ISO-date-separator.¸file-header-ISO-date-separator

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