Home » Date and Time » Date » Bug #4130

[2005-04-12 20:45 UTC] rachelw at cybrzn dot com

Description:
------------
Was using the getWeeksInMonth() function found in Date.php. I noticed the actual function is implemented in Date/Calc.php (Date_Calc class) in the weeksInMonth() method.

Date package version 1.4.3
Date/Calc.php: version 1.2.6
Date.php: version 1.2.8

configure line:
'./configure' '--prefix=/usr' '--with-config-file-path=/etc' '--with-apxs2' '--with-openssl=/usr/local/ssl' '--with-zlib' '--with-bz2' '--with-cpdflib' '--with-curl' '--enable-dba' '--with-db4' '--with-gd' '--with-jpeg-dir=/usr' '--with-png-dir=/usr' '--with-zlib-dir=/usr' '--with-xpm-dir=/usr' '--with-ttf' '--with-freetype-dir=/usr' '--with-gd-native-ttf' '--with-gettext' '--with-imap=../imap-2004' '--with-mcrypt' '--with-mysql' '--with-ncurses' '--with-unixODBC' '--with-snmp' '--with-openssl-dir=/usr/local/ssl' '--with-imap-ssl=/usr/local/ssl' '--enable-ftp' '--with-pspell'

I am writing a dynamically generated calendar, and for the month of May 2005, it returned 6 for the number of weeks in that month, instead of the correct response of 5. Some other months where it returns 6 weeks when it should return 5 include:

August 2004
January 2006
October 2006
April 2007
July 2007

Upon inspecting any similarities between these months, I noticed that the 1st of the month is on Sunday with all of these. Perhaps that might point you in the right direction.

Reproduce code:
---------------
$year = $_GET["year"];
$month = $_GET["month"];

$first_month = new Date($year."-".$month."-01");
$days_month = $first_month->getDaysInMonth();
$weeks_month = $first_month->getWeeksInMonth();

echo $weeks_month; //expect 5 but it returns 6

Expected result:
----------------
again, for these months (just a sampling):

August 2004
May 2005
January 2006
October 2006
April 2007
July 2007

I expect to get a result of 5 (weeks) vs. 6.

Actual result:
--------------
Actual result is 6 (instead of 5).

[2005-04-13 06:44 UTC] pierre at dotgeek dot org

Sorry, but your problem does not imply a bug in PEAR itself. For a
list of more appropriate places to ask for help using PEAR, please
visit http://pear.php.net/support/ as this bug system is not the
appropriate forum for asking support questions.

Thank you for your interest in PEAR.

It's not the ISO definition of a week that is used here.

That means you will get 6 for 05/2005.

ISO defines the 1st week of a month as the one having a tuesday, using it, you will get 5. This behavior will not change in the Date 1.4 series (BC issues).

--Pierre

[2005-04-13 14:17 UTC] rachelw at cybrzn dot com

So why isn't the ISO definition used here? Isn't that what most people think of when they think of how many weeks are in a month? Furthermore, what exactly IS the definition that is being used? How in the world do you get 6 weeks out of a month like May 2005?

[2005-04-13 14:21 UTC] rachelw at cybrzn dot com

Well in the calendar application I'm writing, I need to know how many weeks in a month, based upon whether or not there is even ONE day in that week because it is used to determine how many rows in an HTML table. I guess I will have to write my own function for that (at least one function isn't too bad considering all the other nice functions I can use from the Date package).

[2005-04-13 19:23 UTC] rachelw at cybrzn dot com

One last thing - the following is the PHP comments for the function weeksInMonth(), found in the Date_Calc class. If this was your intention, then it doesn't work properly, because it does not return the correct number of ROWS (i.e. HTML <tr> tags) for outputting a calendar. Any month which begins on a Sunday, and which has 5 weeks (rows), returns 6 instead.

/**
* Returns the number of rows on a calendar month
*
* Useful for determining the number of rows when displaying a typical month calendar.

function weeksInMonth($month = 0, $year = 0)
...

[2005-04-13 19:28 UTC] pierre at dotgeek dot org

Forget to mention that there will be a getIsoWeeksInMonth() or something similar :). No date yet, but move to verified.

--Pierre

[2005-04-13 22:02 UTC] rachelw at cybrzn dot com

It's a quick fix, and perhaps a bit crude, but it worked for me. Hopefully it will help anyone else in a similar situation (please let me know if I should also post this somewhere else):

require_once("Date/Calc.php");

$days_of_week = array("Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday");
$num_days_week = 7;

function weeksInMonth ($month,$year) {
//get the numerical value (0-6) of the first day of the month
$firstDay = Date_Calc::dayOfWeek(01,$month,$year);

//now subtract that value with the # of days in a week, to get the # of days in the first week
$numDaysInFirstWeek = $num_days_week - $firstDay;

//get the # of days in this month
$daysInMonth = Date_Calc::daysInMonth($month,$year);

//get the numerical value (0-6) of the last day of the month
$lastDay = Date_Calc::dayOfWeek($daysInMonth,$month,$year);

//add 1 to that value to get the # of days in the last week
$numDaysInLastWeek = $lastDay+1;

//subtract the # of days in first and last weeks with the # of days in month to get remaining days
$numDaysInOtherWeeks = $daysInMonth - $numDaysInFirstWeek - $numDaysInLastWeek;

//divide the remaining days by # of days in a week, and add the first & last week to get total weeks
return ($numDaysInOtherWeeks / $num_days_week) + 2;
}