sub last_days_first
{ my $i=@_[0];
my $s=86400 * $i;
my ($sec,$min,$hour,$day,$mon,$year,$wday,$yday,$isdst) = localtime(time-$s);
$year+=1900;
$mon+=1;
my $h_first='00';
my $m_first='00';
my $s_first='00';
my $days = sprintf("%04d-%02d-%02d %02d:%02d:%02d",$year,$mon,$day,$h_first,$m_first,$s_first);