The example code below allows for an arbitrary number of lines with an empty 'day' field, it reuses the last non-empty day field read.

#!/usr/bin/perl
use strict;use warnings;

my $day = '';
while (my $line = <DATA>) {
   chomp $line;
   my ($newday,$ptime,$stime,$ctime,$amount) = split /\t/,$line;
   $day = $newday if $newday..$newday;
   print "$day\t$ptime\t$stime\t$ctime\t$amount\n";
   }


__DATA__
01-May-2007     34      11am    567     665
        65      12am    657     4
        64      4pm     345     3
05-May-2007     87      10pm    987     56
06-May-2007     987     9am     8899    765
        567     unkn    4       3
[download]

01-May-2007     34      11am    567     665
01-May-2007     65      12am    657     4
01-May-2007     64      4pm     345     3
05-May-2007     87      10pm    987     56
06-May-2007     987     9am     8899    765
06-May-2007     567     unkn    4       3
[download]