It consists of 52 or 53 full weeks. Please note that there are multiple systems for week numbering, this is the ISO week date standard (ISO-8601), other systems use weeks starting on Sunday (US) or Saturday (Islamic). A precise date is specified by the ISO week-numbering year in the format YYYY, a week number in the format ww prefixed by the letter 'W', and the weekday number, a digit d from 1 through 7, beginning with Monday and ending with Sunday. It allows you to specify whether the week should start on Monday or Sunday and the returned week number should be between 0 and 52 or 0 and 53. I vetted it against a random sample of dates in 2016 and 2015, and passed anything I threw at it. These pages explain how to use week numbers in various popular software applications and programming languages. Instead of having to come up with your own algorithm you can simply do the following in PHP 5.1 and higher: Thanks in advance. One thing I wanted to do was show the data for a quarter, but graphing by day is too chaotic and graphing by month only gives three points, so I wanted to graph by week. First off, from the PHP.net Manual, the ‘W’ inside the date() function returns the week number for a year.. Week ISO-8601 week number of year, weeks starting on Monday (added in PHP 4.1.0) Example: 42 (the 42nd week in the year) A quick example of date(‘W’) See the Pen JavaScript - Get the week start date-date-ex-50 by w3resource (@w3resource) on CodePen. With a return_type of 2, week 1 begins on January 1, and week 2 begins on the next Monday. mode is an optional argument that determines the logic of week number calculation. ). This is the main difference while using MODE between WEEK() function and YEARWEEK() function. … The problem I’ve run into is that “first day of the week” is subjective. All weeks are starting on Monday and ending on Sunday. IntlCalendar::setFirstDayOfWeek (PHP 5 >= 5.5.0, PHP 7, PECL >= 3.0.0a1) IntlCalendar::setFirstDayOfWeek — Set the day on which the week is deemed to start This means that the first day of the year for ISO weeks is always a Monday in the period between Jan 29 and Jan 4. PHP offers the function CODE date("w"); for getting the week of the year - however the week starts on a Monday. A friend asked "How do I calculate start (monday) and end (sunday) dates from a given week number for a specified year?" Getting the week number for a date in PHP is simple. PHP Version: 4+ PHP Changelog: PHP 5.3.0: Relative time formats such as this week, previous week, last week, and next week now interprets a week period of Monday through Sunday, rather then a 7-day period relative to the current date/time PHP 5.3.0: Now 24:00 is a valid format How to find all the Sundays in PHP. See the WEEKNUM page for more information. Prior to PHP 5.6.23, Relative Formats for the start of the week aligned with PHP's (0=Sunday,6=Saturday). I’d do it this way - [code]$weekstart = strtotime("next Monday") - 604800; echo "start of week is: ".date("D M j G:i:s T Y", $weekstart). Write a PHP function to get start and end date of a week (by week number) of a particular year.