39.10.3 Date Formats

Here are some sample diary entries, illustrating different ways of formatting a date. The examples all show dates in American order (month, day, year), but Calendar mode supports European order (day, month, year) as an option.

4/20/93  Switch-over to new tabulation system
apr. 25  Start tabulating annual results
4/30  Results for April are due
*/25  Monthly cycle finishes
Friday  Don't leave without backing up files

The first entry appears only once, on April 20, 1993. The second and third appear every year on the specified dates, and the fourth uses a wildcard (asterisk) for the month, so it appears on the 25th of every month. The final entry appears every week on Friday.

You can use just numbers to express a date, as in ‘month/day’ or ‘month/day/year’. This must be followed by a nondigit. In the date itself, month and day are numbers of one or two digits. The optional year is also a number, and may be abbreviated to the last two digits; that is, you can use ‘11/12/1989’ or ‘11/12/89’.

Dates can also have the form ‘monthname day’ or ‘monthname day, year’, where the month's name can be spelled in full or abbreviated (with or without a period). The preferred abbreviations can be controlled using the variables calendar-abbrev-length, calendar-month-abbrev-array, and calendar-day-abbrev-array. The default is to use the first three letters of a name as its abbreviation. Case is not significant.

A date may be generic; that is, partially unspecified. Then the entry applies to all dates that match the specification. If the date does not contain a year, it is generic and applies to any year. Alternatively, month, day, or year can be a ‘*’; this matches any month, day, or year, respectively. Thus, a diary entry ‘3/*/*’ matches any day in March of any year; so does ‘march *’.

If you prefer the European style of writing dates—in which the day comes before the month—type M-x european-calendar while in the calendar, or set the variable european-calendar-style to t with M-x customize, or before using any calendar or diary command. This mode interprets all dates in the diary in the European manner, and also uses European style for displaying diary dates. (Note that there is no comma after the monthname in the European style.) To go back to the (default) American style of writing dates, type M-x american-calendar.

You can use the name of a day of the week as a generic date which applies to any date falling on that day of the week. You can abbreviate the day of the week to three letters (with or without a period) or spell it in full; case is not significant.