Convert EST to GMT

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

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Re: Convert EST to GMT by CountZero (Bishop) on Nov 04, 2011 at 20:57 UTC
`use Modern::Perl; use DateTime; my $dt = DateTime->new( year => 2011, month => 1, day => 7, hour => 8, minute => 59, second => 54, time_zone => 'America/New_York', ); say $dt->set_time_zone('GMT');` [download] output: `2011-01-07T13:59:54` CountZero A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James	[reply] [d/l] [select]
Re: Convert EST to GMT by ikegami (Patriarch) on Nov 04, 2011 at 21:20 UTC
DateTime::Format::Strptime `use strict; use warnings; use feature qw( say ); use DateTime::Format::Strptime qw( ); my $format = DateTime::Format::Strptime->new( pattern => '%F %T.%3N', locale => 'en', time_zone => 'local', on_error => 'croak', ); my $dt = $format->parse_datetime('2011-01-07 08:59:54.123'); $dt->set_time_zone('UTC'); say $format->format_datetime($dt); # 2011-01-07 13:59:54.123` [download] It's not clear what you mean by 'EST'. Here are the time zones you might be interested in using: 'local' is the same as 'America/New_York' if your machine uses that time zone. 'America/New_York' will actually factor in DST, meaning it will use UTC-4 if the date is in summer and UTC-5 if the date is in winter. Note that your format is ambiguous one hour each year if this is its time zone. '-500' will use UTC-5 for all dates. 'EST' is an ambiguous alias for '-500' (as Australia also has an EST). It's probably best to avoid it.	[reply] [d/l]
Re: Convert EST to GMT by JavaFan (Canon) on Nov 04, 2011 at 20:57 UTC
Some pedantic notes: 1) Transforming from EST to GMT is easy: they always differ 5 hours. But you probably have a time that is either in EST or EDT. 2) EST is an ambiguous name, it could mean Eastern Standard Time, from either North America, or Australia, or it could mean European Summer Time. 3) Without knowing whether the timezone is EST or EDT, there's one hour a year in which you can cannot uniquely map the time to GMT. 4) EDT lasts longer than EST, so most of the time the difference is actually 4 hours. 5) I prefer to use UTC over GMT.	[reply]
Re: Convert EST to GMT by Anonymous Monk on Nov 04, 2011 at 19:53 UTC
http://datetime.perl.org/wiki/datetime/page/FAQ%3A_Time_Zones#If_I_know_my_local_time_how_do_I_determine_the_local_time_in_another_time_zone_-1	[reply]
Re: Convert EST to GMT by DrHyde (Prior) on Nov 08, 2011 at 10:27 UTC
EST is ambiguous - it can be either UTC-5 or UTC+10. Yes Americans, Australians have clocks too! Assuming that you mean the Yankee version, then EST is always 5 hours off from GMT. ALWAYS. If you're interested in daylight "saving" (which, of course, doesn't exist) then you are also interested in EDT and BST. This all gets very complicated, so you should just use DateTime and use unambiguous timezones like Europe/London and America/New_York.	[reply]