X: I want to write timestamps to a text file in a reasonably human-friendly format and then read them back, getting the same epoch second for comparison with localtime.

Y: my first attempt with Time::Piece:

use strict;
use warnings;
use Time::Piece;
use feature 'say';

my $fmt = '%d %b %Y %T %Z';
say localtime->strftime;
say localtime->strftime($fmt);
my $str = '03 Sep 2022 16:10:17 GMT Daylight Time';
my $strtime = Time::Piece->strptime($str, $fmt);
say localtime->epoch;
say $strtime->epoch;

[download]

This returns:

Sat, 03 Sep 2022 16:10:35 GMT Daylight Time
03 Sep 2022 16:10:35 GMT Daylight Time
Garbage at end of string in strptime:  Daylight Time at C:/Strawberry/
+perl/lib/Time/Piece.pm line 598.
Perhaps a format flag did not match the actual input? at C:/Strawberry
+/perl/lib/Time/Piece.pm line 598.
1662217835
1662221417

[download]

This is out by the timezone offset. The docs tell me to look at https://www.unix.com/man-page/FreeBSD/3/strftime/, which says that %z will be treated as a numerical offset. For me, this gives the same as upper case Z, although I can't rule out the influence of Windows on this. DateTime says it won't parse dates and gives no indication I could see of how to handle localtime.

I'd be happy with UTC, but Time::Piece does not seem to support it, which is why I think I may have an XY problem. I can't believe that no-one has invented this wheel, but my searches have been fruitless and all the wheels I have tried seem square. I know that clocks moving back at the end of next month will bite me. All help gratefully received.

Regards,

John Davies

In reply to [Solved] Reading a timestamp and getting the written value by davies

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