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

This is version 0.04 of Regexp::Common::time, May 29, 2008.

 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.

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.

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

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'};

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 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.

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 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.

$RE{time}{ymd}

 "05/4/2"      =~ $RE{time}{ymd};
 "2005-APR-02" =~ $RE{time}{ymd};

This is the most flexible of the numeric-only year/month/day formats. It matches a date of the form "year/month/day", where the year may be 2 or 4 digits; the month may be 1 or 2 digits or a spelled-out name or name abbreviation, and the day may be 1 or 2 digits. The year/month/day elements may be directly adjacent to each other, or may be separated by a space, period, slash (/), or hyphen.

$RE{time}{y4md}

 "2005/4/2"    =~ $RE{time}{y4md};
 "2005 APR 02" =~ $RE{time}{y4md};

This works as $RE{time}{ymd}, except that the year is restricted to be exactly 4 digits.

$RE{time}{y4m2d2}

 "2005/04/02" =~ $RE{time}{y4m2d2};

This works as $RE{time}{ymd}, except that the year is restricted to be exactly 4 digits, and the month and day must be exactly 2 digits each.

$RE{time}{y2md}

 "05/4/2"    =~ $RE{time}{y2md};
 "05.APR.02" =~ $RE{time}{y2md};

This works as $RE{time}{ymd}, except that the year is restricted to be exactly 2 digits.

$RE{time}{y2m2d2}

 "05/04/02" =~ $RE{time}{y2m2d2};

This works as $RE{time}{ymd}, except that the year is restricted to be exactly 2 digits, and the month and day must be exactly 2 digits each.

$RE{time}{YMD}

 "2005/04/02" =~ $RE{time}{YMD};

This is a shorthand for the "canonical" year/month/day format, y4m2d2.

$RE{time}{mdy}

$RE{time}{mdy4}

$RE{time}{m2d2y4}

$RE{time}{mdy2}

$RE{time}{m2d2y2}

$RE{time}{MDY}

These patterns function as the equivalent year/month/day patterns, above; the only difference is the order of the elements. MDY is a synonym for m2d2y4.

$RE{time}{dmy}

$RE{time}{dmy4}

$RE{time}{d2m2y4}

$RE{time}{dmy2}

$RE{time}{d2m2y2}

$RE{time}{DMY}

These patterns function as the equivalent year/month/day patterns, above; the only difference is the order of the elements. DMY is a synonym for d2m2y4.

$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.

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)

 # 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'

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

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.

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.

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

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