Date comparison

[bengmau]

I have 4 strings with date "02/03/08" "02/04/02" I want to compare dates to see which is equal, newer etc.. same for time "3:00pm" and "4:00am" What is the easiest way to compare time and dates?

[ehdonhon]

Take a look at Date::Parse. You can use that to convert them to unix timestamp, and then just do numeric comparison.

[George_Sherston]

ehdonon ++ this is by far the easiest solution, and worth spelling out so that it doesn't get lost in the subsequent controversy

use Date::Parse;
my @dates = qw[ 02/03/08 02/04/02 3:00pm 4:00am ];
my @sorted = sort {str2time($a) <=> str2time($b)} @dates;
print $_,"\n" for @sorted;
__END__
02/04/02
4:00am
3:00pm
02/03/08

- n.b. times are assumed to be *today* unless date is specified. This will handle a variety of different date / time formats.

§ George Sherston

[dws]

Since str2time() is a relatively expensive routine, this a perfect time for pulling out the "Orcish Maneuver".

In the example above, change   my @sorted = sort {str2time($a) <=> str2time($b)} @dates; to

  my %cache;
  my @sorted = sort {($cache{$a} ||= str2time($a)) <=>
                     ($cache{$b} ||= str2time($b)) } @dates;

[Abigail-II]

Use Date::Calc, or if that can't parse it, or if you need very specialized date functions, use Date::Manip.

Abigail

[bengmau]

I tried Date::Manip.. module is too big! I'll try Date parse.. see what I can see..

[thunders]

In my version of Perl Date::Manip weighs in at 211KB which is 1KB less than the wildly popular CGI

[Abigail-II]

What do you mean by "module is too big"? Perl doesn't have any limitations on how large a module can be.

Abigail

[cjf]

Date::Calc should do the job. For your first situation with dates in year/month/day format:

my $string_one = "02/03/08"; # assuming year/month/day
my $string_two = "02/04/02";

my @date_one = split /\//, $string_one;
my @date_two = split /\//, $string_two;

$date_one[0] = 20 . $date_one[0];
$date_two[0] = 20 . $date_two[0];

my $time_one = Date_to_Time(@date_one, 0, 0, 0); # 0s are for hour/min
+/sec
my $time_two = Date_to_Time(@date_two, 0, 0, 0);

if ($time_one > $time_two) {
    print "$time_one is newest.\n";
} elsif ($time_one < $time_two) {
    print "$time_two is newest.\n";
} else {
    print "Same date (to the nearest day).\n";
}

Comparing dates in hour:minuteAM/PM should be simple as well, just split the string for the hour, minute, and AM/PM parts, add 12 to the hours if it contains PM, convert to minutes, and compare.

[joshua]

If you want a module-free way to compare dates, you could look here.

Joshua

[tomhukins]

Others have asked and answered this question here before. Typing date into the search box brings up some relevant posts. You could use Super Search if you require more precise information.