"Should be a simple thing" not going well for me

[TheBigAmbulance]

I'm trying to manipulate a time stamp. The original time is UTC and is stored as 2011-07-24T17:46:33Z I need to convert this from UTC to the Olsen zone "America/North_Dakota/Center". I am using the perl module Date::Manip::Date. I have tried various scripts coming up with this mess

#!/usr/bin/perl -w
use strict;
use warnings;

use Date::Manip::Date;

my $date = "2011-07-24T17:46:33Z";
my $localzone = "America/North_Dakota/Center";

my $err = $date->convert([$localzone]);

print $err;

and I am not getting anywhere to convert this. The desired output is 2011-07-24 12:46:33 PM CDT AND be daylight savings time sensative. Anyone have mercy on this poor soul?

[BrowserUk]

This is wrong:

use Date::Manip::Date;

my $date = "2011-07-24T17:46:33Z";
...
my $err = $date->convert([$localzone]);

Before you can call methods, you first need to create an object:

my $date = new Date::Manip::Date;

Then you need to set the date & time value into that object using the appropriate method(s).

Then you need to invoke the convert method passing a timezone in one of the formats documented within the modules POD.

Try reading the POD.

[Plankton]

This node should be useful to you: Timezone conversion in Perl. See jasonk's reply.

[tye]

Drop the square brackets. I believe they were shown just to indicate that passing in a timezone scalar is optional.

[jandrew]

I prefer DateTime::Format::DateManip over the module you have selected. This provides an object with all the exposed methods allowed for DateTime while still providing some parsing of date strings.

#! C:/Perl/bin/perl
use Modern::Perl;
use DateTime::Format::DateManip;

my  $dt = DateTime::Format::DateManip->parse_datetime( 
               "2011-07-24T17:46:33Z" 
          );
say $dt;
# Lock down the parsed time zone
    $dt->set_time_zone( 'UTC' );
say $dt;
# change the time zone
    $dt->set_time_zone( "America/North_Dakota/Center" );
say $dt;

Output

# 2011-07-24T17:46:33
# 2011-07-24T17:46:33
# 2011-07-24T12:46:33

[sundialsvc4]

Try reading the POD.

/me nods ...

Unfortunately for the OP, BrowerUK’s admonition here is right on the mark.   Click on the link in this sentence to look at the search.cpan.org description of Date::Manip::Date, and you will see, at the very beginning of that page in the SYNOPSIS section, that the too-brief example code uses the module, then instantiates a new object.   Unfortunately the synopsis is not complete:   it does not tell you what to do next.

Objects like these are designed to be instantiated, and then to provide the service of parseing a date string, thus obtaining its value (or throwing an error), and to answer questions about the value, and to print the formatted value.

In a case like this, I find that sometimes the best source of “but how does it actually work?” information is to look at the test-library (a directory t) within the package subdirectory.   Here you will find code that is designed to work as well as code that is designed to fail in certain ways.   Perl runs all of these tests before installing the module permanently.   They can be an excellent source of information, usually written by the author himself.

P.S.:   “Simple things” never are.