use File::Copy;
use Time::Local;

my ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdist) = localtime time;

my $week="daily/Sun-23-Mar-2008/";

.... other code 

#########   daily file creation ########
########################
#create new file for new day @ 1700

if ($hour == 17 && $min ==0 && min !=30)

       { qx(touch $week.$mday); }


#####################
### calculate REAL day
### by subtracting 1 from mday if hour > 00 and < 1700
###  WHATABOUT THE MONTH???

my $filemday = $mday;

if ($hour < 17 && $hour >= 0)

	{ $filemday = $filemday-1; }
my $dayfile = $week.$filemday.".txt";


### print data to file

if (-e $dayfile) { 
		open (DATA,">>$dayfile");
		print DATA ""$hour:$min,some data\n";
		close (DATA);
		}

... other code