Skip to content

Instantly share code, notes, and snippets.

@colindecarlo
Created March 25, 2012 16:26
Show Gist options
  • Save colindecarlo/2198044 to your computer and use it in GitHub Desktop.
Save colindecarlo/2198044 to your computer and use it in GitHub Desktop.
Calculate the last <blank> of the month
<?php
class MyDateTime extends DateTime
{
protected $_daysOfTheWeek = array('sunday', 'monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday');
public function lastDayOfTheMonth()
{
$lastDayOfTheMonth = new MyDateTime($this->format('Y-m-t'), $this->getTimezone());
return $lastDayOfTheMonth;
}
public function lastWeekdayOfTheMonth($weekday)
{
if (false === ($weekdayIndex = array_search(strtolower($weekday), $this->_daysOfTheWeek))) {
throw new Exception("Unknown weekday: " . $weekday);
}
$lastDayOfTheMonth = $this->lastDayOfTheMonth();
$lastWeekday = clone $lastDayOfTheMonth;
if ($lastDayOfTheMonth->format('w') < $weekdayIndex) {
$lastWeekday->sub(new DateInterval('P7D'));
$daysUntil = $weekdayIndex - $lastDayOfTheMonth->format('w');
$lastWeekday->add(new DateInterval(sprintf('P%dD', $daysUntil)));
} else if ($lastDayOfTheMonth->format('w') > $weekdayIndex) {
$daysSince = $lastDayOfTheMonth->format('w') - $weekdayIndex;
$lastWeekday->sub(new DateInterval(sprintf("P%dD", $daysSince)));
}
return $lastWeekday;
}
}
$today = new MyDateTime(null, new DateTimeZone('America/Toronto'));
$lastWednesday = $today->lastWeekdayOfTheMonth('wednesday');
echo $lastWednesday->format('Y-m-d') . "\n";
$april = new MyDateTime('2012-04-01', new DateTimeZone('America/Toronto'));
$lastWednesday = $april->lastWeekdayOfTheMonth('wednesday');
echo $lastWednesday->format('Y-m-d') . "\n";
$october = new MyDateTime('2012-10-01', new DateTimeZone('America/Toronto'));
$lastWednesday = $october->lastWeekdayOfTheMonth('wednesday');
echo $lastWednesday->format('Y-m-d') . "\n";
$september = new MyDateTime('2012-09-01', new DateTimeZone('America/Toronto'));
$lastSunday = $september->lastWeekdayOfTheMonth('sunday');
echo $lastSunday->format('Y-m-d') . "\n";
@JCook21
Copy link

JCook21 commented Mar 26, 2012

format('Y-m-d'); //Of course this is only good if you just want to get the last date of a month. //You'd have to muck about with some cloning, etc if you wanted to go from a start date to the last date of the month. //The following works if you want to work backwards in time: $date = new DateTime('1st April 2012', new DateTimeZone('America/Toronto')); $date->modify('Last Wednesday'); echo $date->format('Y-m-d');

@colindecarlo
Copy link
Author

Abracadabra!

You're right, what you've got there works, but for me, and this is just my opinion, it's got way too much black magic going on. I'm just not a fan of using relative dates like 'yesterday' or 'tomorrow' with strtotime. I just prefer to explicitly modify datetime objects with add() and sub().

@JCook21
Copy link

JCook21 commented Mar 26, 2012

Fair enough-I understand where you're coming from. I'll just keep performing my black magic. :)

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment