Perl Date calculations over two months - mysql

Question

i have a report which runs weekly on a friday doing some db queries where data is from monday to friday and producing a table with the results. I am having a problem when the report runs on a friday where the monday is last month. So for example last friday. Friday was the first of august, and the monday was the 28th of july. The below is the date and time portion of my script.
my $date = `date +%Y%m%d`;
chomp($date);
my $time = `date +%H%M%S`;
chomp($time);
my $day = `date +%A`;
chomp($day);
my $time = `date +%H%M%S`;
chomp($time);
my $dispTime = `date +%H:%M`;
chomp($dispTime);
# Set the Dates
my $end = $date;
my $start = $end;
# Check the day and define start and end dates.
if ($day eq "Friday") {
$start = $end - 5;
my #mytime=localtime;
my ($s, $min, $h, $d, $m, $y) = (0, 0, 0, $mytime[3], $mytime[4], $mytime[5]);
my $todayminus5 = strftime "%Y%m%d", $s, $min, $h, $d - 5, $m, $y;
$start = $todayminus5;
In my report logs it prints the date that was calculated and it printed this
Start Date = 2014080,
End Date = 20140801
Does anybody know why this doesnt seem to be able to calculate the date if its over two months?

Answer 1

You should use Time::Piece in conjunction with its sister module Time::Seconds. If you have a reasonably recent version of Perl then it should already be installed as it has been a core module since version 10 of Perl 5.
By the way, you need to subtract four days to get from Friday to the previous Monday!
use strict;
use warnings;
use Time::Piece;
use Time::Seconds 'ONE_DAY';
my $now = localtime;
if ($now->wdayname eq 'Fri') {
my $monday = ($now - ONE_DAY * 4)->strftime('%Y%m%d');
# etc.
}

Answer 2

I would rework the approach you're taking - you're doing multiple invocations of date which is probably a warning sign in the first place. You've got a whole lot of edge cases - subtracting '5' from your days will get you a negative number if it's early in the month - which will break things - but you'll have similar problems when the year changes.
I won't contradict the previous post, but I'd instead suggest you simplify:
my $ONE_DAY_s = 60 * 60 * 24;
my $now = time();
my $then = $now - 4*$ONE_DAY_s;
my ( $sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime($now);
$year += 1900;
print "Now: $year $mon $mday\n";
( $sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime($then);
$year += 1900;
print "Then: $year $mon $mday\n";
(transcribed, rather than pasted so beware typos).
You can use $wday to figure out if it's a friday.
Modules exist to do this as well though - I would be very wary of using repeated invocations of an external command, and then trying to mangle the results.

Answer 3

You can use the Datetime module to get the start date and end date
Example:
use strict;
use warnings;
use DateTime;
my $today_date = DateTime->today(); # Current date (Friday)
my $old_date = $today_date->clone()->subtract(days => 4); # First DoW (Monday)
print $today_date, "\n";
print $old_date, "\n";
Outputs:
2014-08-04T00:00:00
2014-07-31T00:00:00