How to parse a string into a DateTime object in Perl? - perl

Question

I know about the DateTime Perl module, and many of the DateTime::Format:: modules to parse specific kinds of date/time formats. However given some examples of date/time strings, how can I figure out (at coding/design time, not at runtime) which specific module should I use?
For example, I want to parse strings like: October 28, 2011 9:00 PM PDT
Is there a list somewhere of the most common date/time formats where I could look this up and find which would be the most suitable module?
I also know about some modules which try to "guess" the format for each given string at runtime and do their best. But, for sensitive applications, I would like to determine (as strictly as possible) the format first when designing an application, and then use a module which will warn me if a string does not match the specified format.
How should I go about this?

Answer 1

DateTime::Format::Strptime takes date/time strings and parses them into DateTime objects.
#!/usr/bin/perl
use strict;
use warnings;
use DateTime::Format::Strptime;
my $parser = DateTime::Format::Strptime->new(
pattern => '%B %d, %Y %I:%M %p %Z',
on_error => 'croak',
);
my $dt = $parser->parse_datetime('October 28, 2011 9:00 PM PDT');
print "$dt\n";
The character sequences used in the pattern are POSIX standard. See 'man strftime' for details.

Answer 2

I tend to use Time::Piece simply because it's part of the standard Perl module set since version 5.10.
You can't beat it's ability to parse date strings.
my $time = Time::Piece->strptime(
"October 28, 2011 9:00 PM PDT",
"%B %d, %Y %r %Z");

Answer 3

Have a look at the Date::Parse module, i.e. the str2time() function. It has support for most of the commonly used formats.
Example:
use Date::Parse;
use DateTime;
my $str = "Tue, 20 Sep 2011 08:51:08 -0500";
my $epoch = str2time($str);
my $datetime = DateTime->from_epoch(epoch => $epoch);

Answer 4

If you are looking for common date/time formats
have a look at DateTime::Locale
use DateTime::Locale
my $locale = DateTime::Locale->load('DE_de');
The following methods return strings appropriate for the DateTime->format_cldr() method:
$locale->date_format_full()
$locale->date_format_long()
$locale->date_format_medium()
$locale->date_format_short()
$locale->date_format_default()
$locale->time_format_full()
$locale->time_format_long()
$locale->time_format_medium()
$locale->time_format_short()
$locale->time_format_default()
$locale->datetime_format_full()
$locale->datetime_format_long()
$locale->datetime_format_medium()
$locale->datetime_format_short()
$locale->datetime_format_default()
You can parse Dates with the DateTime::Format::CLDR module
use DateTime::Format::CLDR;
# 1. Basic example
my $cldr = DateTime::Format::CLDR->new(
pattern => 'dd.MM.yyyy HH:mm:ss',
locale => 'de_DE',
time_zone => 'Europe/Berlin',
);
my $dt = $cldr->parse_datetime('26.06.2013 11:05:28');

Answer 5

DateTime::Format::Natural is also a good candidate.
Test:
perl -MDateTime::Format::Natural \
-E "my $d=DateTime::Format::Natural->new->parse_datetime('October 11, 2021'); say $d->month;"
10