This is the input file, and it has combination of GMT dates.

74.13.151.1     -       -       [22/Jun/2010:06:00:00   +0000]  GET
67.195.112.248  -       -       [21/Jun/2010:20:09:42   +0000]  GET
99.138.106.5    -       -       [21/Jun/2010:23:10:18   +0000]  GET
99.138.106.5    -       -       [21/Jun/2010:09:10:18   +0000]  GET
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When I run the script using the code below.

#!/usr/bin/perl

use strict;
use warnings;

use Date::Manip;
my $date_converted = UnixDate(ParseDate("3 days ago"),"%e/%h/%Y");
open DATA,">$ARGV[1]";
open FH,"$ARGV[0]";

while(<FH>){
  my @tab_delimited_array = split(/\t/,$_);
  $tab_delimited_array[3] =~ s/^\[//;
  $tab_delimited_array[3] =~ s/^\-//;
  chomp($tab_delimited_array[3]);

    if(length($tab_delimited_array[3]) > 1)
     {
    my $date_format = UnixDate($tab_delimited_array[3],"%Y%m%d%H:%M:%S
+");
    my $converted_date = Date_ConvTZ("$date_format",'GMT','PST');
    my $pst_converted_date = UnixDate($converted_date,"%e/%h/%Y:%H:%M:
+%S");
     $pst_converted_date =~ s/^\s//g;
    my $extracted_YMD=UnixDate($converted_date,"%e/%h/%Y");
     $_ =~ s/$tab_delimited_array[3]/$pst_converted_date/g;
if($extracted_YMD =~ m/$date_converted/){
        print DATA $_;
        }
    }
}

close DATA;
close FH;
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output is

74.13.151.1     -       -       [21/Jun/2010:22:00:00   +0000]  GET
67.195.112.248  -       -       [21/Jun/2010:12:09:42   +0000]  GET
99.138.106.5    -       -       [21/Jun/2010:15:10:18   +0000]  GET
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When I use the code,it is matching the input file for just 3 days ago.

my $target = UnixDate(Date_ConvTZ( ParseDate("3 days ago"), 'GMT', 'PS
+T' ),"%e/%h/%Y");
print $target;
open DATA,">$ARGV[1]";
open FH,"$ARGV[0]";

m/\[$target:/ and print DATA $_ while <FH>;
close DATA;
close FH;
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Output is:

67.195.112.248  -       -       [21/Jun/2010:20:09:42   +0000]  GET
99.138.106.5    -       -       [21/Jun/2010:23:10:18   +0000]  GET
[download]

please tell me how to optimize the code to read the date/time from input file and convert to PST time.

while(<FH>){
  my @tab_delimited_array = split(/\t/,$_);
  $tab_delimited_array[3] =~ s/^\[//;
  $tab_delimited_array[3] =~ s/^\-//;
  chomp($tab_delimited_array[3]);

    if(length($tab_delimited_array[3]) > 1)
     {
    my $date_format = UnixDate($tab_delimited_array[3],"%Y%m%d%H:%M:%S
+");
    my $converted_date = Date_ConvTZ("$date_format",'GMT','PST');
    my $pst_converted_date = UnixDate($converted_date,"%e/%h/%Y:%H:%M:
+%S");
     $pst_converted_date =~ s/^\s//g;
    my $extracted_YMD=UnixDate($converted_date,"%e/%h/%Y");
     $_ =~ s/$tab_delimited_array[3]/$pst_converted_date/g;
if($extracted_YMD =~ m/$date_converted/){
        print DATA $_;
        }
    }
}
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