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.