jacwright/date.format — pull request #7 by BlackWiCKED (2014-08-19 22:56:38+00:00)
Title: Fixed week number calculator, to meet ISO 8601 standard.

It should fix issue #6, I reused the code from webpage: http://techblog.procurios.nl/k/news/view/33796/14863/calculate-iso-8601-week-and-year-in-javascript.html