I suspect what you are looking for is a hash of arrays. The following code may get you headed in the right direction:

use strict;
use warnings;

my %dailyRecords;

while (<DATA>) {
    chomp;
    next if ! length;
    
    my @record = split; # Pull out the data fields

    # Pull out Date and generate a date stamp
    my @now = reverse ((localtime ($record[1]))[3..5]);
    my $dateStamp = join '', map {sprintf '%04d', $_} @now;
    
    # Append this record to list keyed by date stamp
    push @{$dailyRecords{$dateStamp}}, [@record];
}

for (sort keys %dailyRecords) {
    print "Day stamp: $_\n";
    my @daysRecords = @{$dailyRecords{$_}};
    
    print "@$_\n" for @daysRecords;
}

__DATA__
1149621887      1149623161  NG004193@net.NET    3       820     156  1
+7570249
1149621900      1149623197  NG004193@net.NET    1       648     80   0
+0      
1149692376      1149694912  NG004193@net.NET    3       7932259 243  8
+5227944
1149695677      1149695693  Sinkbad@net.net     1       49385   0    0
+0
[download]

Prints:

Day stamp: 010600050007
1149621887 1149623161 NG004193@net.NET 3 820 156 17570249
1149621900 1149623197 NG004193@net.NET 1 648 80 00
Day stamp: 010600050008
1149692376 1149694912 NG004193@net.NET 3 7932259 243 85227944
1149695677 1149695693 Sinkbad@net.net 1 49385 0 00
[download]