Convert dates in 'dd/MM/yy' format to 'MMM-YY'. Excel returns wrong year

Hi

I have a column "A" in a table with dates in my country format "dd/MM/yy".
in the column "B" I want to have the dates in the previous column in the format "MMM-YY", so I can display the data in a pivot table.

so I used a loop in VBA with 'Format('cellInColumn_A', "MMM-YY")' to fill column "B"
For some reason, Excel returns the wrong year in the "MMM-YY" format:

"A" -> "B"
Date -> "MMM-YY"
13/01/15 -> (15/01/16) shows 'Jan-16'
01/01/15 -> (15/01/16) shows 'Jan-16'
25/08/15 -> (15/08/16) shows 'Aug-16', etc, etc

I have tried to change the date format to "dd/MM/yyyy" to enforce the year, but the result is the same.

What am I doing wrong?
Thanks
Luis