How to Calculate Week Number of the Year from a Specific Date in PHP?


You want to find out the week number from a date that you have.


You can find out week number from a date in few ways. Let’s see 2 of those-

Method 1: Using format() method of DateTime class from SPL.

Calculating week number from a date using DateTime class is 2 steps process.

  1. Create a DateTime Object from your specific date
  2. Use the format() method to find out the week number using the “W” format character.

The following shows the code –

$date = "2014-06-03";
$dateObj = new DateTime($date);
$weekNumber = $dateObj->format("W");
echo "The week nummer of $date is: ". $weekNumber;

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The week number of 2014-06-03 is: 23

How it works:

Line 2 The date with which we’ll work.
Line 3 We create a DateTIme object($dateObj) from the date.
Line 4 As we’re only interested in the week number, we use “W” in the format() method which will return the week number of the date that from the DateTIme object, $dateObj. We store the week number in the $weekNumber variable. Please note that the format() method accepts the format parameter strings that the date() method use. See the List of format characters.
Line 5 We prints the output.


Method 2: Using strtotime() function

Using strtotime() to find out the week number is also 2 steps process-

  1. Convert your date to its equivalent timestamp. The timestamp of a date is number of seconds since January 1 1970 00:00:00 UTC.
  2. From the timestamp, we’ll find out the week number using date() function with “W” format string. The format character “W” returns the week number of year.

See the following example-

$date = "2014-06-03";
$timestamp = strtotime($date);
echo "The week nummer of $date is: " . date("W", $timestamp);

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The week nummer of 2014-06-03 is: 23