w3c date('h:i:s', code example

Example 1: date in php

Things to be aware of when using week numbers with years.

<?php
echo date("YW", strtotime("2011-01-07")); // gives 201101
echo date("YW", strtotime("2011-12-31")); // gives 201152
echo date("YW", strtotime("2011-01-01")); // gives 201152 too
?>

BUT

<?php
echo date("oW", strtotime("2011-01-07")); // gives 201101
echo date("oW", strtotime("2011-12-31")); // gives 201152
echo date("oW", strtotime("2011-01-01")); // gives 201052 (Year is different than previous example)
?>

Reason:
Y is year from the date
o is ISO-8601 year number
W is ISO-8601 week number of year

Conclusion:
if using 'W' for the week number use 'o' for the year.

Example 2: date in php

<?php
// set the default timezone to use. Available since PHP 5.1
date_default_timezone_set('UTC');


// Prints something like: Monday
echo date("l");

// Prints something like: Monday 8th of August 2005 03:12:46 PM
echo date('l jS \of F Y h:i:s A');

// Prints: July 1, 2000 is on a Saturday
echo "July 1, 2000 is on a " . date("l", mktime(0, 0, 0, 7, 1, 2000));

/* use the constants in the format parameter */
// prints something like: Wed, 25 Sep 2013 15:28:57 -0700
echo date(DATE_RFC2822);

// prints something like: 2000-07-01T00:00:00+00:00
echo date(DATE_ATOM, mktime(0, 0, 0, 7, 1, 2000));
?>