Time Convert Question

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Hi there Monks!
I am trying to convert a time to my time zone "America/New_York", but somehow the code is taking the time I am converting to and subtracting instead of adding to it. Here is the code:

#!/usr/bin/perl -w

use strict;
use DateTime;
use DateTime::TimeZone;
use DateTime::Format::MySQL;

my $somewhere_time = "2011-06-09 08:19:12"; # pacific time?
my $dt = DateTime::Format::MySQL->parse_datetime($somewhere_time);
   $dt->set_time_zone('UTC');
   $dt->set_time_zone('America/New_York');

print DateTime::Format::MySQL->format_datetime($dt),"\n";
# I should be expecting to get: 2011-06-09 10:19:12
[download]

Any thoughts?
Thanks!

Comment on Time Convert Question Download Code

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Re: Time Convert Question by MidLifeXis (Monsignor) on Jun 09, 2011 at 16:04 UTC
What time are you actually getting? If it works as you are assuming ($somewhere_time, as initialized, in UTC), and the sequential set_time_zone calls assign the original time to UTC and then convert it to NY, I would expect it to show as 04:19:12, not 10:19:12. NY is currently -0400 (behind UTC), not +0200. This assumes that the first call to `set_time_zone` sets the initial time zone, and the second converts it to NY. What value are you actually seeing? --MidLifeXis	[reply] [d/l]
Re^2: Time Convert Question by Anonymous Monk on Jun 09, 2011 at 17:16 UTC
You are right, I am getting "2011-06-09 04:19:12"	[reply]
Re^2: Time Convert Question by Anonymous Monk on Jun 09, 2011 at 17:32 UTC
How would a set this to the right time zone, "NY is currently -0400 (behind UTC), not +0200", thanks for your response.	[reply]
Re^3: Time Convert Question by MidLifeXis (Monsignor) on Jun 09, 2011 at 17:51 UTC
Given the other example on this thread, it appears that the first time zone assigned to a floating time is adopted as the time's TZ. Assign the TZ for the floating time value to wherever that value was generated. For all we know, the timezone for that string could be the Aleutian Islands, Anchorage, Alaska, Tokyo, London, or Timbuktu. Until there is something to anchor it to, you cannot do a comparison that has any meaning. --MidLifeXis	[reply]
Re: Time Convert Question by Anonymous Monk on Jun 09, 2011 at 16:50 UTC
The timestamp you're parsing doesn't contain timezone information #!/usr/bin/perl -- use warnings; use strict; use DateTime; use DateTime::TimeZone; use DateTime::Format::MySQL; my @Tzs = ( 'America/Los_Angeles', 'UTC', 'America/New_York', ); my $somewhere_time = "2011-06-09 08:19:12"; # pacific time? my $dt = DateTime::Format::MySQL->parse_datetime($somewhere_time); print $dt->_TZLP; Tzss( $dt ); print ' ' x 21, DateTime::Format::MySQL->format_datetime($dt),"\n\n"; # I should be expecting to get: 2011-06-09 10:19:12 Tzss( DateTime->now ); sub Tzss { my $dt = shift; for my $tz ( @Tzs ) { $dt->set_time_zone( $tz ); print $dt->_TZLP; } } sub DateTime::_TZLP { sprintf "%-20s %s\n", $_[0]->time_zone_long_name, $_[0]->strftime("%F %T%z"); } __END__ floating 2011-06-09 08:19:12+0000 America/Los_Angeles 2011-06-09 08:19:12-0700 UTC 2011-06-09 15:19:12+0000 America/New_York 2011-06-09 11:19:12-0400 2011-06-09 11:19:12 America/Los_Angeles 2011-06-09 09:43:52-0700 UTC 2011-06-09 16:43:52+0000 America/New_York 2011-06-09 12:43:52-0400 [download]	[reply] [d/l]
Re^2: Time Convert Question by Anonymous Monk on Jun 09, 2011 at 18:27 UTC
Actually a quick fix to this is to add this line at the beginning of the Perl code: `$ENV{'TZ'} = 'America/New_York';` [download] How's that!?	[reply] [d/l]
Re^3: Time Convert Question by Anonymous Monk on Jun 10, 2011 at 06:37 UTC
How's that!? What are you hoping to accomplish with that? America/New_York is not pacific time	[reply]