How do I convert date format between 'DD-MM-YYYY' and 'YYYY-MM-DD' back & forth?

[naikonta]

I provide a field for user to type in a date string, mostly in 'DD-MM-YYYY' format, and store it later in MySQL database, which uses 'YYYY-MM-DD' format. But sometimes, users use different separators such as slashes and dots. And in the edit form I have to display the date back to its original form. How do I do that? (Assume the input is in valid date range.)

Originally posted as a Categorized Question.

[jettero]

use Date::Manip:

my $date = UnixDate( ParseDate($thingy), '%Y-%m-%d' );

[naikonta]

Well, basically, just reverse the date components in the list and put it back as string.

my $in_date = '30-04-2007';
my $db_date = join '-', reverse split '-', $in_date;

# to get the original format, do the same thing
my $pr_date = join '-', reverse split '-', $db_date;
print "in: $in_date; db: $db_date; pr: $pr_date\n";
# in: 30-04-2007; db: 2007-04-30; pr: 30-04-2007

For multi-possible-separator, use the non-digit character class for split().

my $in_date = '02/05/2007'; # or 02.05.2007, or any non-digit-separato
+rs
my $db_date = join '-', reverse split /\D/, $in_date;

# to get the original format, do the same thing as before
my $sep = '-';
my $pr_date = join $sep, reverse split '-', $db_date;
print "in: $in_date; db: $db_date; pr: $pr_date\n";
# in: 02/05/2007; db: 2007-05-02; pr: 02-05-2007

In this situation, there's no way to convert the date back with its original separator unless you kept it somewhere somehow, if that really matters. Besides, this might be a good chance to enforce your standard separator :-)

[naikonta]

The following answer uses regexes.

# UK-style
my $in_date = '30-04-2007';
(my $db_date = $in_date) =~ s/(\d\d)-(\d\d)-(\d\d\d\d)/$3-$2-$1/;
(my $pr_date = $db_date) =~ s/(\d\d\d\d)-(\d\d)-(\d\d)/$3-$2-$1/;
print "in: $in_date; db: $db_date; pr: $pr_date\n";
# in: 30-04-2007; db: 2007-04-30; pr: 30-04-2007

# US-style
my $in_date = '05-14-2007';
(my $db_date = $in_date) =~ s/(\d\d)-(\d\d)-(\d\d\d\d)/$3-$1-$2/;
(my $pr_date = $db_date) =~ s/(\d\d\d\d)-(\d\d)-(\d\d)/$2-$3-$1/;
print "in: $in_date; db: $db_date; pr: $pr_date\n";
# in: 05-14-2007; db: 2007-05-14; pr: 05-14-2007

Instead of rolling your own, some CPAN modules might help, such as Date::Tiny, Date::Formatter, or Date::Simple. They look promising but I haven't tried them myself.

[naikonta]

Just in case you specify that the date must be in US-style (MM-DD-YYYY), then the above split won't work.

my $in_date = '11-24-2007'; # or 11/24/2007, or 11.24.2007, or any non
+-digit-separators
my @parts = split /\D/, $in_date;
my $db_date = join '-', @parts[2, 0, 1];

# to get the original format:
my $sep = '-';
my @parts = split $sep, $db_date;
my $pr_date = join $sep, @parts[1, 2, 0];
print "in: $in_date; db: $db_date; pr: $pr_date\n";
# in: 11-24-2007; db: 2007-11-24; pr: 11-24-2007