NAME¶

Regexp::Common::time - Date and time regexps.

SYNOPSIS¶

 use Regexp::Common qw(time);
 # Piecemeal, Time::Format-like patterns
 $RE{time}{tf}{-pat => 'pattern'}
 # Piecemeal, strftime-like patterns
 $RE{time}{strftime}{-pat => 'pattern'}
 # Match ISO8601-style date/time strings
 $RE{time}{iso}
 # Match RFC2822-style date/time strings
 $RE{time}{mail}
 $RE{time}{MAIL}    # more-strict matching
 # Match informal American date strings
 $RE{time}{american}
 # Fuzzy date patterns
 #               YEAR/MONTH/DAY
 $RE{time}{ymd}         # Most flexible
 $RE{time}{YMD}         # Strictest (equivalent to y4m2d2)
                 # Other available patterns: y2md, y4md, y2m2d2, y4m2d2
 #               MONTH/DAY/YEAR  (American style)
 $RE{time}{mdy}         # Most flexible
 $RE{time}{MDY}         # Strictest (equivalent to m2d2y4)
                 # Other available patterns: mdy2, mdy4, m2d2y2, m2d2y4
 #               DAY/MONTH/YEAR  (European style)
 $RE{time}{mdy}         # Most flexible
 $RE{time}{MDY}         # Strictest (equivalent to d2m2y4)
                 # Other available patterns: dmy2, dmy4, d2m2y2, d2m2y4
 # Fuzzy time pattern
 #               HOUR/MINUTE/SECOND
 $RE{time}{hms}    # H: matches 1 or 2 digits; 12 or 24 hours
                   # M: matches 2 digits.
                   # S: matches 2 digits; may be omitted
                   # May be followed by "a", "am", "p.m.", etc.

DESCRIPTION¶

This module creates regular expressions that can be used for parsing dates and times. See Regexp::Common for a general description of how to use this interface.

Parsing dates is a dirty business. Dates are generally specified in one of three possible orders: year/month/day, month/day/year, or day/month/year. Years can be specified with four digits or with two digits (with assumptions made about the century). Months can be specified as one digit, two digits, as a spelled-out name, or as a three-letter abbreviation. Day numbers can be one digit or two digits, with limits depending on the month (and, in the case of February, even the year). Also, different people use different punctuation for separating the various elements.

A human can easily recognize that "October 21, 2005" and "21.10.05" refer to the same date, but it's tricky to get a program to come to the same conclusion. This module attempts to make it possible to do so, with a minimum of difficulty.

• If you know the exact format of the data to be matched, use one of the specific, piecemeal pattern builders: "tf" or "strftime".
• If you are parsing RFC-2822 mail headers, use the "mail" pattern.
• If you are parsing informal American dates, use the "american" pattern.
• If there is some variability in your input data, use one of the fuzzy-matching patterns in the "dmy", "mdy", or "ymd" families.
• If the data are wildly variable, such as raw user input, you should probably give up and use Date::Manip or Date::Parse.

Time values are generally much simpler to parse than date values. Only one fuzzy pattern is provided, and it should suffice for most needs.

Time::Format PATTERNS¶

The Time::Format module uses simple, intuitive strings for specifying date and time formats. You can use these patterns here as well. See Time::Format for details about its format specifiers.

Example:

    $str = 'Thu November 2, 2005';
    $str =~ $RE{time}{tf}{-pat => 'Day Month d, yyyy'};

The patterns can contain more complex regexp expressions as well:

    $str =~ $RE{time}{tf}{-pat => '(Weekday|Day) (Month|Mon) d, yyyy'};

Time zone matching (the "tz" format code) attempts to adhere to RFC2822 and ISO8601 as much as possible. The following time zones are matched:

    Z
    UT        UTC
    +hh:mm    -hh:mm
    +hhmm     -hhmm
    +hh       -hh
    GMT   EST EDT   CST CDT   MST MDT   PST PDT

strftime PATTERNS¶

The POSIX "strftime" function is a long-recognized standard for formatting dates and times. This module supports most of "stftime"'s codes for matching; specifically, the "aAbBcCDdeHIjmMnprRSTtuUVwWyxXYZ%" codes. The %Z format matches time zones in the same manner as described above under "Time::Format PATTERNS".

Also, this module provides the following nonstandard codes:

" %_d -" 1- or 2-digit day number (1-31)

" %_H -" 1- or 2-digit hour (0-23)

" %_I -" 1- or 2-digit hour (1-12)

" %_m -" 1- or 2-digit month number (1-12)

" %_M -" 1- or 2-digit minute (0-59)

Example:

    $str = 'Thu November 2, 2005';
    $str =~ $RE{time}{strftime}{-pat => '%a %B %_d, %Y'};

The patterns can contain more complex regexp expressions as well:

    $str =~ $RE{time}{strftime}{-pat => '(%A|%a)? (%B|%b) ?%_d, %Y'};

ISO-8601 DATE/TIME MATCHING¶

The $RE{time}{iso} pattern will match most (all?) strings formatted as recommended by ISO-8601. The canonical ISO-8601 form is:

    YYYY-MM-DDTHH:MM:SS

(where ""T"" is a literal T character). The $RE{time}{iso} pattern will match this form, and some variants:

• The date separator character may be a hyphen, slash ("/"), period, or empty string (omitted). The two date separators must match.
• The time separator character may be a colon, a period, a space, or empty string (omitted). The two time separators must match.
• The date-time separator may be a "T", an underscore, a space, or empty string (omitted).
• Either the date or the time may be omitted. But at least one must be there.
• If the date is not omitted, all three of its components must be present.
• If the time is not omitted, all three of its components must be present.

RFC 2822 MATCHING¶

RFC 2822 specifies the format of date/time values in e-mail message headers. In a nutshell, the format is:

    dd Mon yyyy hh:mm:ss +zzzz

where "dd" is the day of the month; "Mon" is the abbreviated month name (apparently always in English); "yyyy" is the year; "hh:mm:ss" is the time; and "+zzzz" is the time zone, generally specified as an offset from GMT.

RFC 2822 requires that the weekday also be specified, but this module ignores the weekday, as it is redundant and only supplied for human readability.

RFC 2822 requires that older, obsolete date forms be allowed as well; for example, alphanumeric time zone codes (e.g. EDT). This module's "mail" allows for these obsolete date forms. If you want to match only the proper date forms recommended by RFC 2822, you can use the "MAIL" pattern instead.

In either case, "mail" or "MAIL", the pattern generated is very flexible about whitespace. The main differences are: with "MAIL", two-digit years are not permitted, and the time zone must be four digits preceded by a + or - sign.

INFORMAL AMERICAN MATCHING¶

People in North America, particularly in the United States, are fond of specifying dates as "Month dd, yyyy", or sometimes with a two-digit year and apostrophe: "Month dd, 'yy". The "american" pattern matches this style of date. It allows either a month name or abbreviation, and is flexible with respect to commas and whitespace.

FUZZY PATTERN OVERVIEW¶

Fuzzy date patterns have the following properties in common:

• The pattern names consist of the letters "y", "m", and "d", each optionally followed by a digit (2 for "m" and "d"; 2 or 4 for "y").
• If a "y" is followed by a 2 or a 4, it must match that many digits.
• If a "y" has no trailing digit, it can match either 2 or 4 digits, trying 4 first.
• If an "m" is followed by a 2, then only two-digit matches for the month are considered, and month names are not matched.
• If an "m" is not followed by a 2, then the month may be 1 or 2 digits, or a spelled-out name.
• Just like for months, if a "d" is followed by a 2, then only two-digit matches for the day are considered.
• Just like for months, if a "d" has no trailing digit, then the day may be 1 or 2 digits, and a 1-digit match may not have any adjacent digits.
• The uppercase "DMY", "MDY", and "YMD" patterns are synonyms for the strict "d2m2y4", "m2d2y4", and "y4m2d2" patterns, respectively.
• If a one-digit match is considered for the month, then no adjacent digits are allowed. (e.g.: "1/23/45" in M/D/Y format has a valid one-digit month match, but "12345" does not. Nor does "91/23/45").
• If a pattern begins with an digitless "d", "m", or "y", then, in the string to be matched, any leading digits will cause the pattern to fail. For example: "012/23/45" will not match $RE{time}{mdy}. However, it will match $RE{time}{m2d2y2}. If you specify an exact pattern by using "m2" instead of "m", this module assumes you know what you're doing.
• Likewise, a pattern ending with a digitless "d" or "y" will not match if there are trailing digits in the string.

FUZZY PATTERN DETAILS¶

Time pattern (Hour-minute-second)¶

$RE{time}{hms}

 "10:06:12a" =~ /$RE{time}{hms}/;
 "9:00 p.m." =~ /$RE{time}{hms}/;
    

Matches a time value in a string.

The hour must be in the range 0 to 24. The minute and second values must be in the range 0 to 59, and must be two digits (i.e., they must have leading zeroes if less than 10).

The hour, minute, and second components may be separated by colons (":"), periods, or spaces.

The "seconds" value may be omitted.

The time may be followed by an "am/pm" indicator; that is, one of the following values:

  a   am   a.m.  p   pm   p.m.   A   AM   A.M.  P   PM   P.M.
    

There may be a space between the time and the am/pm indicator.

CAPTURES (-keep)¶

Under "-keep", the "tf" and "strftime" patterns capture the entire match as $1, plus one capture variable for each format specifier. However, if your pattern contains any parentheses, "tf" and "strftime" will not capture anything additional beyond what you specify, "-keep" or not. In other words: if you use parentheses, you are responsible for all capturing.

The "iso" pattern captures:

" $1 -" the entire match

" $2 -" the year

" $3 -" the month

" $4 -" the day

" $5 -" the hour

" $6 -" the minute

" $7 -" the second

The year, month, and day ($2, $3, and $4) will be "undef" if the matched string contains only a time value (e.g., "12:34:56"). The hour, minute, and second ($5, $6, and $7) will be "undef" if the matched string contains only a date value (e.g., "2005-01-23").

The "mail" and "MAIL" patterns capture:

" $1 -" the entire match

" $2 -" the day

" $3 -" the month

" $4 -" the year

" $5 -" the hour

" $6 -" the minute

" $7 -" the second

" $8 -" the time zone

The "american" pattern captures:

" $1 -" the entire match

" $2 -" the month

" $3 -" the day

" $4 -" the year

The fuzzy y/m/d patterns capture

" $1 -" the entire match

" $2 -" the year

" $3 -" the month

" $4 -" the day

The fuzzy m/d/y patterns capture

" $1 -" the entire match

" $2 -" the month

" $3 -" the day

" $4 -" the year

The fuzzy d/m/y patterns capture

" $1 -" the entire match

" $2 -" the day

" $3 -" the month

" $4 -" the year

The fuzzy h/m/s pattern captures

" $1 -" the entire match

" $2 -" the hour

" $3 -" the minute

" $4 -" the second ("undef" if omitted)

" $5 -" the am/pm indicator ("undef" if omitted)

EXAMPLES¶

 # Typical usage: parsing a data record.
 #
 $rec = "blah blah 2005/10/21 blah blarrrrrgh";
 @date = $rec =~ m{^blah blah $RE{time}{YMD}{-keep}};
 # or
 @date = $rec =~ m{^blah blah $RE{time}{tf}{-pat=>'yyyy/mm/dd'}{-keep}};
 # or
 @date = $rec =~ m{^blah blah $RE{time}{strftime}{-pat=>'%Y/%m/%d'}{-keep}};
 # Typical usage: parsing variable-format data.
 #
 use Time::Normalize;
 $record = "10-SEP-2005";
 # This block tries M-D-Y first, then D-M-Y, then Y-M-D
 my $matched;
 foreach my $pattern (qw(mdy dmy ymd))
 {
     @values = $record =~ /^$RE{time}{$pattern}{-keep}/
         or next;
     $matched = $pattern;
 }
 if ($matched)
 {
     eval{ ($year, $month, $day) = normalize_rct($matched, @values) };
     if ($@)
     {
         .... # handle erroneous data
     }
 }
 else
 {
     .... # no match
 }
 #
 # $day is now 10; $month is now 09; $year is now 2005.
 # Time examples
 $time = '9:10pm';
 @time_data = $time =~ /$RE{time}{hms}{-keep}/;
 # captures '9:10pm', '9', '10', undef, 'pm'
 @time_data = $time =~ /$RE{time}{tf}{-pat => '(h):(mm)(:ss)?(am)?'}{-keep}/;
 # captures '9', '10', undef, 'pm'

EXPORTS¶

This module exports no symbols to the caller's namespace.

SEE ALSO¶

It's not enough that the date regexps can match various formats. You then have to parse those matched data values and translate them into useful values. The Time::Normalize module is highly recommended for performing this repetitive, error-prone task.

REQUIREMENTS¶

Requires Regexp::Common, of course.

If POSIX and I18N::Langinfo are available, this module will use them; otherwise, it will use hardcoded English values for month and weekday names.

Test::More is required for the test suite.

AUTHOR¶

Eric J. Roode, ROODE -at- cpan -dot- org

LICENSE AND COPYRIGHT¶

Copyright (c) 2005-2008 by Eric J. Roode, ROODE -at- cpan -dot- org

All rights reserved.

To avoid my spam filter, please include "Perl", "module", or this module's name in the message's subject line, and/or GPG-sign your message.

This module is copyrighted only to ensure proper attribution of authorship and to ensure that it remains available to all. This module is free, open-source software. This module may be freely used for any purpose, commercial, public, or private, provided that proper credit is given, and that no more-restrictive license is applied to derivative (not dependent) works.

Substantial efforts have been made to ensure that this software meets high quality standards; however, no guarantee can be made that there are no undiscovered bugs, and no warranty is made as to suitability to any given use, including merchantability. Should this module cause your house to burn down, your dog to collapse, your heart-lung machine to fail, your spouse to desert you, or George Bush to be re-elected, I can offer only my sincere sympathy and apologies, and promise to endeavor to improve the software.