For a project I am working on we need to know the week number which is displayed via a date form field widget in the admin section.

On the front end we also show the week number but we are using a jQuery UI datepicker, however these two datepickers are showing different week numbers. This week starting 15/6/2015 is shown as week 25 in jQuery UI and is week 24 in Magento admin date picker.

After some investigation I have found jQuery is using ISO 8601 week date standards to determine the first week of the year.

I am still not sure what format Magento is using but it seems to have some errors displaying at years end/start when I look ahead years.

I am hoping for some setting or fix that I can implement to bring Magento date picker in line with jQuery UI and ISO 8601, I could do the reverse but prefer to follow ISO 8601 standards.

2 Answers 2


After some further investigation I found that both where trying to calculate the week using the ISO 8601 standard. Magento appears to have a bug in how it was calculating it which was caused by a bug in the JS that runs the calendar used in the admin section of magento.

The file is js/calendar/calendar.js on line 1187

cell.innerHTML = date.getWeekNumber();

The calls to get the week number of the first day of the week (default Sunday). However the function 'getWeekNumber' gets the week number of the nearest Thursday which for a Sunday is the Thursday of the previous week.

To fix this I changed this to find the week number of the Thursday of the current line rather than the first day of the week.

var tday = new CalendarDateObject(date);
if(date.getDay() > 4){
  tday.setDate(tday.getDate() + (7 - (date.getDay() - 4)));
} else if (date.getDay() < 4){
  tday.setDate(tday.getDate() + (4 - date.getDay()));
cell.innerHTML = tday.getWeekNumber();

As this file is a core file, editing it may be overwritten by a future upgrade of Magento. However I've not yet found a way to fix this without overwriting this js file.

  • mark your answer as right answer to help other. Commented Jun 19, 2015 at 1:14

Change the parameters in this file js/calendar-setup.js





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