I need help with extracting the week number and year from a certain date in excel and I don't get the correct information when a week contains different years. I am using this formula:

=CONCATENATE(YEAR(A2)," ",TEXT(WEEKNUM(A2,21),"00"))

and I get these results:

12/31/2015: 2015 53

1/1/2016: 2016 53

The result for 1/1/2016 should be 2015 53 as week 1 2016 starts on 1/4/2016 as per the European system.

Can somebody help me how to get the correct result?

Thanks!