As a followup on date calculations, here’s small one to calculate the number of days between two dates, the same disclamer as for the previous post applies, so, without further ado, here goes:

# Given two dates, calculate the number of days between them
sub diff_dates {
  my ($sec1,$min1,$hour1,$mday1,$mon1,$year1) = @_[0..5];
  my ($sec2,$min2,$hour2,$mday2,$mon2,$year2) = @_[6..11];
  my $time1 = timegm($sec1,$min1,$hour1,$mday1,$mon1,$year1);
  my $time2 = timegm($sec2,$min2,$hour2,$mday2,$mon2,$year2);
  my $diff_seconds = $time1 - $time2;
  my $daydiff = $diff_seconds / 24 / 3600;

  return int( $daydiff );
}

Tags: computing, linkedin, perl

Ok, here’s a small snippet for calculating a new date given a date and the numer of days forward or backwards from that date without having to include Date::Time or some other big date handling lib which is not part of the standard perl distro. It wouldn’t surprise me if there are some subtile problems with this way of doing it, maybe leap years or something will mess it up, but I have found that it works fine for the most for me at least YMMV!

The format of the input is of course according to timegm.

# Given a date and the number of days forward or backwards (negative) calculate that date
sub calc_date {
  my ($sec,$min,$hour,$mday,$mon,$year) = @_[0..5];
  my $diff_days = $_[6];
  my $time = timegm($sec,$min,$hour,$mday,$mon,$year);
  my $diff_seconds = $diff_days * 24 * 3600;
  my $end_time = $time + $diff_seconds;

  return localtime($end_time);
}

Tags: computing, linkedin, perl