Biz Week offers you a handy calendar with the capability to show you the week number given the date, or viceversa, and lets you create an event for that date in the device native calendar, directly from the app, preparing for you most of the typical fields of the event mask.
A badge showing the week number associated to the selected date will show next to the icon, in the home screen.
IMPORTANT NOTE:
Biz Week adheres to the standard ISO 8601, used in most of the European countries, where weeks start from Mondays.