use Time::Local qw( timegm );

my ($y1,$m1,$d1) = (1985,12,25);
my ($y2,$m2,$d2) = (2005,2,4);

my $t1 = timegm(0,0,0,$d1,$m1-1,$y1);
my $t2 = timegm(0,0,0,$d2,$m2-1,$y2);

my $days = ($t2-$t1)/(24*60*60);
print("$days\n");  # 6981