$ perl -MTime::Piece -MTime::Seconds -Mstrict -Mwarnings -E '
my $dateStr = q{2016-05-16 00:51:07};
my $dateFmt = q{%Y-%m-%d %H:%M:%S};
my $tp      = Time::Piece->strptime( $dateStr, $dateFmt );
$tp        -= ONE_HOUR;
say $tp->strftime( $dateFmt );'
2016-05-15 23:51:07
$