#!/usr/bin/perl -w 
use strict;

my $table={};
while(my $line=<DATA>){
     chop $line;
     my ($name,$date,$time,$value)=split(/[\s]+/,$line);
     my $key = $date . "-" . $time; 
     if ( ! defined($table->{$key}) { 
          $table->{$key}={ name => '', min => 99999999, max => 0 };
     } 
     $table->{$key}->{min} = $value if $value < $table->{$key}->{min}
     $table->{$key}->{max} = $value if $value > $table -> {$key}->{max}
}

foreach my $key (sort keys %$table){
    my ($date,$time) = split("-",$key);
    printf "Date: %s   Time: %s   max = %d  min = %d\n",$date,$time,
               $table->{$key}->{max},
               $table->{$key}->{min};
}

exit(0);

__END__
fred            9/1/2011     15:00:00   50
mary            9/1/2011     15:00:00   0
john            9/1/2011     15:00:00   16