title: Unique month-year combinations in excel/google spreadsheets
body: <p>I have one column (A) with dates and I want to create a column with unique month-year.</p>
  
  <p>I could use the UNIQUE function but that requires creating an extra column (B) with:
  <code>= DATE(YEAR(A1),MONTH(A1))</code> and the final column <code>= UNIQUE(B1:B)</code></p>
  
  <p>The question is, can I do it without creating the extra column?</p>