Formula for What year it was the previous week

Does anyone know a formula that would display what the 'year' it was the 'previous week'?

So for example, last week,(which was week 1 of 2013), the formula would have shown year '2012'. (for week 52 of 2012)
This week the formula would show '2013'.

Thanks

What formula do you use to determine the week number? The problem probably lies therein. Here's an excellent link where you can find multiple ways to display the proper week number.

http://www.cpearson.com/excel/WeekNumbers.aspx