Automating InDesign with Regular Expressions

4.1. Dates

Dates are great for trying regexes because they are short strings with much internal variation: 29 September 2006; 29 Sept. 2006; September 28th, 2006; Sept. 29th, 2006; 29-10-2006; 29-10-06; 10-29-2006; 10-29-06; and the last four can be written with slashes or dots instead of hyphens. The regular expression:

/\d\d-\d\d-\d\d\d\d/g

matches 29-10-2006 and 10-29-2006 in the list. To match single-digit days and months as well, we simply make the second digit in each optional; to capture years written in four or two digits, we make the last two digits optional. The regex in the following script matches all date formats written in digits:

var txt = 'the date 29-1-2006 is memorable';
txt.match( /\d?\d-\d?\d-\d\d(\d\d)?/g );

Another type of variation in date formats is the separator, which can be a hyphen, a slash, or a dot. To account for slashes, hyphens, and dots as separator, we define them as a class:

/\d?\d[-\/\.]\d?\d[-\/\.]\d\d(\d\d)?/

Matching dates when the months are written in full is a bit trickier. To match the 23 September or Sept. 2006, for example, we need something like the following:

/\d\d? [A-Z][a-z]+\.? \d\d\d\d/

looking for one or two digits (\d\d?) followed by a space, followed by a word starting with an upper-case letter, possibly ending with a period (\.?, to capture abbreviated month names; note the escaped dot), followed by four digits. To match September 23rd, 2006, another regex is needed. Something like this:

 /[A-Z][a-z]+ \d?\d(st|nd|rd|th), ...