将历史时间戳从 UTC 转换为本地

Question

我有一个文件，其中包含过去的时间戳，并且都是 UTC 时间。我需要将这些转换为东部时间。我已经接近了，但它在夏令时转换期间搞砸了。

#!/usr/bin/perl
use strict;
use warnings;
use Time::Piece;

#DST not in effect
my $utc = '2015-03-08 01:59:00.000';
my $local = utc_to_local($utc);
print "DST not in effect: utc($utc) = local($local)\n";

#DST not in effect
$utc = '2015-03-08 02:00:00.000';
$local = utc_to_local($utc);
print "DST not in effect: utc($utc) = local($local)\n";


sub utc_to_local
{
    my $utc_ts = $_[0]; #this has ms on right side, we want left 19 characters
    $utc_ts = substr $utc_ts, 0, 19;
    my $local_tp = localtime->strptime( $utc_ts, '%Y-%m-%d %H:%M:%S' );
    $local_tp = $local_tp + $local_tp->tzoffset();

    return $local_tp->strftime('%Y-%m-%d %H:%M:%S');
}

如您所见，如果我在 3 月 8 日尝试 1:59 AM UTC 并在 3 月 8 日尝试 2 AM UTC，它认为更改已经发生，但 2 AM UTC 只有 3/7晚上 9 点。远离夏令时转换，它会正确执行 -5 和 -4 偏移。

DST not in effect: utc(2015-03-08 01:59:00.000) = local(2015-03-07 20:59:00)
DST not in effect: utc(2015-03-08 02:00:00.000) = local(2015-03-07 22:00:00)

Answer 1

$utc_ts 不是当地时间。

my $local_tp = localtime->strptime( $utc_ts, '%Y-%m-%d %H:%M:%S' );

应该是

my $utc_tp = Time::Piece->strptime( $utc_ts, '%Y-%m-%d %H:%M:%S' );

然后是转换为本地时间的问题。

$local_tp = $local_tp + $local_tp->tzoffset();

应该是

my $local_tp = localtime($utc_tp->epoch);

总计：

#!/usr/bin/perl
use strict;
use warnings;
use POSIX qw( );
use Time::Piece;

sub utc_to_local {
    my ($utc_ts) = @_;
    my $utc_tp = Time::Piece->strptime( $utc_ts, '%Y-%m-%d %H:%M:%S' );
    my $local_tp = localtime($utc_tp->epoch);
    return $local_tp->strftime('%Y-%m-%d %H:%M:%S');
}

sub local_to_utc {
    my ($local_ts) = @_;
    my $local_tp = Time::Piece->strptime( $local_ts, '%Y-%m-%d %H:%M:%S' );
    my $utc_tp = gmtime($local_tp->epoch);
    return $utc_tp->strftime('%Y-%m-%d %H:%M:%S');
}

{
    $ENV{TZ} = 'America/Toronto';
    POSIX::tzset();

    # DST not in effect
    my $utc = '2015-03-08 06:59:00.000';
    my $local = utc_to_local(substr($utc, 0, -4));
    print "DST not in effect: utc($utc) = local($local)\n";

    # DST not in effect
    $utc = '2015-03-08 07:00:00.000';
    $local = utc_to_local(substr($utc, 0, -4));
    print "DST not in effect: utc($utc) = local($local)\n";
}

输出：

DST not in effect: utc(2015-03-08 06:59:00.000) = local(2015-03-08 01:59:00)
DST not in effect: utc(2015-03-08 07:00:00.000) = local(2015-03-08 03:00:00)

将历史时间戳从 UTC 转换为本地

Converting Historical Timestamps from UTC to Local

perl

utc