how to convert from a calendar date to an ordinal date with out any modules

Question

I need to search for a time range in a log file. The time stamps are in JDE Julian date format and I cannot use modules.

The date format is YYYYJJJHHMMSS where JJJ is the days in Julian.

I need to convert the user input in JDE with out using a module.

Answer 1

The fact that these number are date/time values makes no difference. They are integers (albeit rather large ones) and they can be compared in exactly the same way as any other integer.

while (<$your_input_filehandle>) {
  # I have no idea of the format of your input data, so I can't
  # begin to implement extract_timestamp()
  my $this_records_timestamp = extract_timestamp($_);

  if ($this_records_timestamp >= $min_timestamp and
      $this_records_timestamp <= $max_timestamp) {
    # timestamp is within the given range
  }
}

Update: To convert YYYYMMDD to YYYYJJ

#!/usr/bin/perl

use strict;
use warnings;
use 5.010;

use Time::Piece;

my $in_format  = '%Y%m%d';
my $out_format = '%Y%j';

my $in_date = shift
  || die "Please pass date in format YYYYMMDD\n";

my $date = Time::Piece->strptime($in_date, $in_format);

say $date->strftime($out_format);