converting time zone CET Greenwitch

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

I am doing some timezone conversions, and I am realizing that this has some cavetas I am not understanding. In this particular case I am trying to convert from CET to Greenwitch. This is one hour difference, yet this script gives me two. It has probably to do with summer/wintertime? Which is the best approach to have precise conversions?

use DateTime;
use DateTime::Format::Strptime;

my $db_update_time = '2024-04-07 15:03:27';

my $parser = DateTime::Format::Strptime->new(
                pattern   => '%Y-%m-%d %T',
                locale    => 'en_US',
                time_zone => 'Europe/Berlin',
                on_error  => 'croak',
);

my $datetime = $parser->parse_datetime($db_update_time);
$datetime->set_time_zone('Greenwich');
$formatted_time = $datetime->strftime('%Y-%m-%d %T');

print $formatted_time;
#output: 2024-04-07 13:03:27
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Comment on converting time zone CET Greenwitch Download Code

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Re: converting time zone CET Greenwitch (summertime) by LanX (Saint) on Apr 07, 2024 at 13:42 UTC
Probably not the cause, but I'm noticing some typos concerning Greenwi(t)ch Edit You are asking for the current time in Berlin - which is summer time CEST- and are comparing it to winter time GMT in London. Both Berlin (CET -> CEST) and London (GMT -> BST) switched to daylight saving time last weekend and are now again 1 h apart. But Greenwich Mean Time aka GMT (UTC+0) is British time in winter, which is 1h apart from Central European (winter) Time CET. I hope it's clear now, that you never got CET in the first place, but CEST. 2 weeks ago your code would have seemingly "worked". Cheers Rolf _{(addicted to the Perl Programming Language :) see Wikisyntax for the Monastery}	[reply]
Re: converting time zone CET Greenwitch by Takamoto (Monk) on Apr 07, 2024 at 13:34 UTC
I am probably confusing Greenwich timezone with Europe/London timezone (Greenwich is in London), since I get correctly 1 hr difference by using `$datetime->set_time_zone('Europe/London');` instead of Greenwich.	[reply] [d/l]
Re^2: converting time zone CET Greenwitch by hippo (Archbishop) on Apr 07, 2024 at 13:43 UTC
Yes, you are correct. London local time is BST (GMT + 1) between the last Sunday in March and the last Sunday in October. The rest of the year it is GMT. 🦛	[reply]

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