I'm using the latest Time::Piece, 1.31

I'm using 1.31_04 and at least in that, strftime works for me for your second spin (which as the only one using localtime makes sense):

#!/usr/bin/env perl

use strict;
use warnings;
use Time::Local;
use Time::Piece;

my $datestr = '2017-06-19 10:07:42-0700';
print "Original date string: $datestr\n\n";

print "Using Time::Local\n";
my $time = timelocal(42, 7, 10, 19, 6, 2017);
print "  Epoch seconds: $time\n";
print "  CORE::localtime: ", scalar CORE::localtime($time), "\n";
print "\n";

print "Using Time::Piece:\n";

print "  strptime as static method:\n";
my $obj = Time::Piece->strptime($datestr, '%Y-%m-%d %H:%M:%S%z');
print "     stringified: $obj\n";
print "     datetime: ", $obj->datetime, "\n";
print "     tzoffset: ", $obj->tzoffset, "\n";
print "     hour: ", $obj->hour, "\n";
print "     strftime: ", $obj->strftime, "\n";

print "  strptime as localtime instance method:\n";
$obj = localtime->strptime($datestr, '%Y-%m-%d %H:%M:%S%z');
print "     stringified: $obj\n";
print "     datetime: ", $obj->datetime, "\n";
print "     tzoffset: ", $obj->tzoffset, "\n";
print "     hour: ", $obj->hour, "\n";
print "     strftime: ", $obj->strftime, "\n"; # Has non-UTC timezone 
+- yay!

print "  strptime as gmtime instance method:\n";
$obj = gmtime->strptime($datestr, '%Y-%m-%d %H:%M:%S%z');
print "     stringified: $obj\n";
print "     datetime: ", $obj->datetime, "\n";
print "     tzoffset: ", $obj->tzoffset, "\n";
print "     hour: ", $obj->hour, "\n";
print "     strftime: ", $obj->strftime, "\n";
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BTW, are you aware that the 2 dates you are using are a month apart?