You could use Time::Piece and Time::Seconds which are core modules in recent Perl versions.

$ perl -MTime::Piece -MTime::Seconds -Mstrict -Mwarnings -E '
my $dateStr = q{2016-05-16 10:51:07};
my $dateFmt = q{%Y-%m-%d %H:%M:%S};
my $tp      = Time::Piece->strptime( $dateStr, $dateFmt );
$tp        -= ONE_HOUR;
say $tp->strftime( $dateFmt );'
2016-05-16 09:51:07
$
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I hope this is helpful.