RE: converting dates to epoch seconds and back

[twlewis]

Bill, it appears to have to do with it pick the time not being populated, and 
it picking up the date from yesterday.

I added some lines to test this theory.  Try running the code below without an 
argument, and then with an argument.

Tim


#!/usr/bin/perl

use strict;
use warnings;
use Time::Local;

my ($time, $month, $day, $year, $seconds, $minutes, $hours, $wday, $yday, 
$isdst);

my $start_date = '11/30/2012';

print $start_date \n;

($month, $day, $year) = split(/\//, $start_date);

#Added this to populate the time
if (defined($ARGV[0])) {
  print Populating the time\n;
  $seconds = 30;
  $minutes = 30;
  $hours = 11;
}

print $time = timegm($seconds, $minutes, $hours, $day, $month-1, $year-1900);

print \n;

($seconds, $minutes, $hours, $day, $month, $year, $wday, $yday, $isdst) = 
localtime($time);

$month++;

$year = ($year+1900);

print $month/$day/$year \n;



-Original Message-
From: Bill Stephenson bi...@ezinvoice.com
Sent: Friday, January 18, 2013 3:13pm
To: Perl Beginners beginners@perl.org
Subject: converting dates to epoch seconds and back

When converting DMYHMS to Epoch Seconds and back I get cheated out of a day. 
Why?

Bill

--

#!/usr/bin/perl

use strict;
use warnings;
use Time::Local;

my ($time, $month, $day, $year, $seconds, $minutes, $hours, $wday, $yday, 
$isdst);

my $start_date = '11/30/2012';

print $start_date \n;

($month, $day, $year) = split(/\//, $start_date);

print $time = timegm($seconds, $minutes, $hours, $day, $month-1, $year-1900);

print \n;

($seconds, $minutes, $hours, $day, $month, $year, $wday, $yday, $isdst) = 
localtime($time);

$month++;

$year = ($year+1900);

print $month/$day/$year \n;

# output:
# 11/30/2012 
# 1354233600
# 11/29/2012
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Re: converting dates to epoch seconds and back

[Dominik Danter]

The output depends on the timezone that you have set on your machine. You can
toy around and try different ones with
$ENV{TZ} = 'Europe/Vienna'; or
$ENV{TZ} = 'America/Los_Angeles';

If you don't want to depend on the timezone use gmtime instead of localtime.

Bill Stephenson bi...@ezinvoice.com hat am 18. Januar 2013 um 21:13
geschrieben:
 When converting DMYHMS to Epoch Seconds and back I get cheated out of a day.
 Why?

 Bill

 --

 #!/usr/bin/perl

 use strict;
 use warnings;
 use Time::Local;

 my ($time, $month, $day, $year, $seconds, $minutes, $hours, $wday, $yday,
 $isdst);

 my $start_date = '11/30/2012';

 print $start_date \n;

 ($month, $day, $year) = split(/\//, $start_date);

 print $time = timegm($seconds, $minutes, $hours, $day, $month-1, $year-1900);

 print \n;

 ($seconds, $minutes, $hours, $day, $month, $year, $wday, $yday, $isdst) =
 localtime($time);

 $month++;

 $year = ($year+1900);

 print $month/$day/$year \n;

 # output:
 # 11/30/2012
 # 1354233600
 # 11/29/2012
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Dominik Danter

Re: converting dates to epoch seconds and back

[John W. Krahn]

Bill Stephenson wrote:

When converting DMYHMS to Epoch Seconds and back I get cheated out of a day. 
Why?

Bill

--

#!/usr/bin/perl

use strict;
use warnings;
use Time::Local;

my ($time, $month, $day, $year, $seconds, $minutes, $hours, $wday, $yday, 
$isdst);

my $start_date = '11/30/2012';

print $start_date \n;

($month, $day, $year) = split(/\//, $start_date);

print $time = timegm($seconds, $minutes, $hours, $day, $month-1, $year-1900);

^^
**



print \n;

($seconds, $minutes, $hours, $day, $month, $year, $wday, $yday, $isdst) = 
localtime($time);


 ^

 *




$month++;

$year = ($year+1900);

print $month/$day/$year \n;

# output:
# 11/30/2012
# 1354233600
# 11/29/2012


You are using GMT for one conversion and local time for the other.  Best 
to use GMT for both conversions:


$ perl -le'
use strict;
use warnings;
use Time::Local;

my ( $time, $month, $day, $year, $seconds, $minutes, $hours );
my $start_date = q[11/30/2012];
print $start_date;
( $month, $day, $year ) = split /\//, $start_date;
print $time = timegm( $seconds, $minutes, $hours, $day, $month - 1, 
$year - 1900 );

( $seconds, $minutes, $hours, $day, $month, $year ) = gmtime $time;
$month++;
$year += 1900;
print $month/$day/$year;
'
11/30/2012
1354233600
11/30/2012




John
--
Any intelligent fool can make things bigger and
more complex... It takes a touch of genius -
and a lot of courage to move in the opposite
direction.   -- Albert Einstein

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