Early reminders for first Monday of month events

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© October 2012 Anthony Lawrence

2012/10/20

I help run a monthly Computer Club meeting in our community. The club actually meets twice per month, once for a general meeting and once to offer troubleshooting services to members of the community.

I keep forgetting to put meeting notices in our community newsletter.

That sounds like a job for a calendar program, doesn't it? Yeah, that's what I thought too, so I fired up Google Calendar and added the two dates for the first Monday and the first Wednesday of every month. So far, so good and now all I had to do was to tell it to remind me at an appropriate time.

Unfortunately, I ran into an immediate problem. I need to get notices to the newsletter editor very early. If I want something to be in the December newsletter, I need to send it in before the first of November. Google Calendar won't let you set a reminder more than one month earlier than an event. If I try to set it for 5 weeks or 32 days, it won't allow that. That's dumb, but there it is: Google doesn't think you'd ever need more than 4 weeks advance notice for anything.

Perl to the rescue

So, I turned to Perl.

There are many ways to approach this in Perl. You could take a brute force approach, setting the date to December 1st, testing to see if that is a Monday and incrementing to December 2d and beyond if it is not. That's actually not such a terrible way to do it as the date we want has to be before the 8th, so there cannot be many iterations.

#!/usr/bin/perl
use Time::Local;

($day,$month,$year)=(localtime)[3,4,5];
$month+=2;
if ($month > 11) {
  $month=0; $year++;
}
$nextmonth=timelocal(0,0,0,1,$month,$year);
$dow=(localtime $nextmonth)[6];
while ($dow != 1) {
 $nextmonth+=24 * 60 * 60;
 $dow=(localtime $nextmonth)[6];
}

print scalar localtime $nextmonth, "\n";;
 

If you ran that on the 28th of each month, you'd have the first Monday of the 2d month following. Add some code to send email and you are done.

Date::Calc

I decided to use Date::Calc instead. It's probably no faster (it might even be slower) and it very likely uses a brute force approach itself, but it has a lot of useful functions (68, in fact) beyond just what we need to do here.

Installing Date::Calc is, however, a somewhat lengthy procedure. It's a lot of code with a whole army of dependencies and it will keep CPAN busy for quite a little while. It will be worth it, though, as our code becomes as simple as:

  ($year,$month,$day) = Today();
  ($year,$month,$day) = Add_Delta_YMD($year,$month,$day, 0,2,0);
  $monday=Nth_Weekday_of_Month_Year($year,$month,1,1);
 

We just need to wrap that up in some formatting and we're ready to put it in crontab:

10      6       28      *       *       /mybin/remindme 2>&1 > /dev/null
 

I'll run it on the 28th of each month and it will send me a reminder email that is ready for any last many editing before being forwarded along to the newsletter.

#!/usr/bin/perl
# "remindme" Tony Lawrence October 2012
# I'm going to run this on the 28th of the month
# I want to know the first Monday and First Wednesday of TWO months ahead
#
use Date::Calc qw( Today Date_to_Days Add_Delta_YMD Decode_Date_US Nth_Weekday_of_Month_Year );
@day=("1st","2d","3rd","4th","5th","6th","7th");
@months=("January","February", "March", "April", "May", "June", "July", "August", "September", "October", "November","December");

  ($year,$month,$day) = Today();
  ($year,$month,$day) = Add_Delta_YMD($year,$month,$day, 0,2,0);
  $monday=Nth_Weekday_of_Month_Year($year,$month,1,1);
  $monday=~ s/$year$month//;
  $wednesday=Nth_Weekday_of_Month_Year($year,$month,3,1);
  $wednesday=~ s/$year$month//;

open(SENT,"|/opt/kerio/mailserver/sendmail tony\@aplawrence.com");
print SENT <<EOF;
Mime-Version: 1.0
Content-Type: text/html
Content-Transfer-Encoding: 8BIT
From: tony\@aplawrence.com
Subject: Computer club schedule for $months[$month-1] $year

<h2>Oak Point Computer Club $months[$month-1] $year</h2>

<p>The Oak Point Computer Club meets on the first Monday and the first Wednesday of every month.</p>

<ul>
<li>The Monday $months[$month-1] $day[$monday-1] meeting is at 2:00 PM in the Back Ballroom.</li>

<li>The Wednesday $months[$month-1] $day[$wednesday-1] meeting is at 5:00 PM in the Back Ballroom.</li>
</ul>

<p>Wednesday is Troubleshooting.  Bring us your problems and questions and we will try to help. First come, first served.</p>

<p>Monday is usually a lecture or informal discussion on some subject.</p>
<p><b>Not just for computer geeks!</b></p>
<p>All Oak Point homeowners are welcome; there are no dues or charges of any kind.</p>
EOF
exit 0;
 

This is the result:

That should help me get my notices to the newsletter on time.

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Got something to add? Send me email.

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